[MUSIC PLAYING]
IAN: All right, folks.
Welcome back to week
six, where we're going
to talk a little bit about exposure.
So to this date we've talked a lot about
composition, lensing, storytelling,
without focusing too much on
the technical details of how
to actually make an image, and
match it to our intentions.
So we'll dive a little
bit more in that today.
And I think it's important
to define exposure.
So the idea of exposure
is that we want to render
a scene in a specific way using
our camera controls to interpret
the amount of light in a given scene.
So what does that really mean?
Well we're going to dive
deep into this, and we're
going to look at each of the
different camera controls.
How they affect the image,
and how we can utilize
them to make different exposures.
So what's our goal
with exposing an image?
It's really to capture
that intentional image.
It's to make a decision about
how we want an image to look
before we press the shutter button.
When you have a camera that's on auto
mode and you press the shutter button
you're basically giving up all the
decision making to a small machine.
And they're sophisticated, sure,
but they're not intelligent.
And our goal is for us
as intelligent operators
to make the decisions for
the camera, or at least
override decisions that may be poor.
So I think what we
really need to understand
is what exactly is it
that we're trying to do?
And so in any given scene
there's some amount of light.
And we can use absolute measurements
to tell how much that is.
It could be 150 foot candles of light,
but I don't know what that means.
I sort of conceptually understand that,
but it doesn't help me take a camera
and make an image.
I have to do a bunch of math.
It gets very confusing.
There's easier ways.
So what we really need is
a relative amount of light,
or at least the scale--
a relative scale that we can use
to adjust our camera settings.
So for us in this class when
we're talking about photography,
and then later cinematography, we're
going to use the concept of f-stops.
And all an f-stop is is a
doubling or halving unit.
So if you have a camera
that has some sensitivity,
and you double the sensitivity
of it, that's one stop.
If you have a camera that has
some light coming into it,
and you cut the amount of light coming
into it by one half, that's one stop.
They're going in opposite
directions, but it's
an equivalent unit of one stop.
So just briefly to get
a sense of how this
might look when we look at an image we
have here an image from Mount Auburn
Cemetery that's at exposure, roughly.
And I made this exposure using
a DSLR, and the light meter
that was in the camera told me that
if I set the camera settings to this
it'll be at exposure.
And I think it did a pretty good job.
There's no real complaints there.
So in an effort to sort of investigate
how much difference a stop might be
I opened up one stop.
So I allowed double the amount
of light to strike the sensor.
And you can see that
it gets much brighter.
If we go backwards we have some dark
shadow detail in here, neutral gray,
some bright white, and
everything feels naturalistic.
We start to brighten up
that neutral gray begins
to push towards the lighter gray,
this definitely begins to clip,
these trees feel a little bit brighter.
Not completely unnatural,
but getting there.
So now if we allow four times
as much light in, or two stops--
remember that you're doubling
each time you open up a stop.
So you double, and
then you double again.
Now this image really
starts to fall apart.
And this is the classic overexposure
that maybe you've accidentally done,
or you've been struggling
with your camera controls.
And you end up here where you have
clipping elements, there's no detail,
there's no actual shadow detail.
No dark tones in this at all.
It's all light grays.
And if we go even further
it completely falls apart.
And we could keep opening this--
allowing more light to hit
the camera and eventually we'd
end up with a solid white image.
So, OK, that's overexposure.
But when we look at this image again--
add exposure.
This is the same image
from the beginning.
And we go the other
way, I've now reduced
the amount of light entering into
the camera by a half, or one stop.
And you can see that all the
tonalities get depressed.
They're getting pushed
down into the shadow areas.
There's more detail in that white
snow, which was much brighter before,
but now it's sort of a shade of gray.
And if we keep going two
stops so four times less light
is reaching in the sensor you now
see like beautiful detail in here,
but everything else is turning into
a muddy, crushed, shadowy darkness.
And if we keep going it
becomes almost unreadable.
So all that is is to say
that we have these tools that
allow us to increase and
decrease the amount of light,
and we do so by measuring it
in doubling or having units.
So how do we measure light?
Well, we have a brief video online that
we posted earlier this week, on Friday,
on light meters, which if
you've all watched, great.
And if not we'll talk a little
bit about as a refresher.
But there's a few different ways.
You can use a handheld light
meter like this to measure light,
but I think more often
than not what we'll use
is the internal light
meter of the camera.
And so this will measure the amount
of light that's striking the subject,
and reflecting back through
the lens onto some sort
of light sensitive material.
And it will say if you set your
camera to these values you'll
get a decent exposure.
So they can be hand-held
or internal to a camera,
but all light meters
are calibrated to expose
for an idea called 18% reflective gray.
And they do so in different ways.
So briefly, before we look
at a couple different ways
they do that, 18% reflective
gray is often sort
of colloquially termed middle gray.
When exposed properly it forms the
middle value between absolute light
and absolute black in your image.
It's right in the middle.
So it's a very handy
reference tone for us.
And it's usually found on a gray card--
something like this, that reflects
back 18% of the light that strikes it.
Cool.
So before we get here let
us quickly fire this guy up.
So this is the output
of our camera right now.
If we take a middle gray
card and we place it
in front of the camera
well illuminated--
we'll fill the frame with it.
We can see that in the middle
of this there's this histogram,
and sort of all of the image data
is centered right in the middle.
If we set it for this
white background you
can see that it's sort of drifted
back to the middle as well.
And that's sort of
interesting because we would
expect this tone to reflect more light.
So there is a bit of a trick going
on with reflective light meters
that we need to pay attention to.
Reflected light meters always
assume that every single element
that they're metering is middle gray.
So there's a problem when you
meter something that is not
middle gray like this white background.
And so if we actually are
to open up this camera
and allow a little bit more light in--
what am I doing here?
There we go.
I has auto ISO on.
So there's the shadow.
Let's get this shadow
out of here so we can--
so now all of a sudden we brighten the
image up by allowing more light in,
and this tone is rendering
normally or as we would wish it to.
So we can also do the same
thing if we have a black object.
You can see that the camera
using the reflective meter
set this value to add
exposure, which is lining up
that small cursor with
the caret in that scale.
You can see that this is not black.
It's middle gray.
It's actually rendering this incorrectly
because what it's expecting to see
is this middle gray card.
So what we need to do
in order to offset that
is actually underexpose
what the camera is reading.
So now when we check this the camera
is like you're over three stops
underexposed, but this
starts to look correct.
So we talked a lot about
this-- thanks, Ben.
[INAUDIBLE]-- in the light meter video.
And we'll come back to this, but that
is to say that in any given scene
the exposure suggested by a
camera is made to be 90% accurate.
Most scenes have a mix of light values,
dark values, and values in between.
So if you sort of assume that that
all melds down to about middle gray
you can suggest an exposure.
And the meter will suggest
an exposure, and then
when you expose for that
you'll be pretty accurate.
But so this scene here is
pretty much all highlights.
And my camera said if you
set it to these settings
you'll get a properly
exposed image, but it's not.
It's too dark.
So if we open up one stop.
Well, we're getting closer.
Snow starting to look like snow.
And if we open up one more stop
maybe we're a little bit too far.
It's getting a little bit bright
over in this area over here,
but it's rendering as
a very bright white.
And sort of side by side
you can see it here.
The metered exposure versus compensating
by increasing our exposure one stop.
So this is what I mean to say when I
say that we need to be a little bit more
intelligent than the machines.
They're very sophisticated.
They can measure all kinds of things,
but they're still sort of locked in
and reference at specific values.
So we need to understand
what those are so
that we can compensate, and
sort of use our intention
to override the camera when it's
making, essentially, a dumb decision.
Yeah?
AUDIENCE: If middle gray
is meant to be halfway
between pure black and pure white
how come it's 18% and not 50?
IAN: So it has to do
with the sensitivity of--
or the way that human eyes render
light, and because it's logarithmic.
So it's a power function.
So 50% is not quite
halfway on a linear scale
when it gets transformed,
I think, but essentially it
is because if you have say--
this is a good example.
If you have one light
bulb, and you turn it on,
and you add another
light bulb it's almost
like you've doubled the
amount of brightness,
and it's a very obvious difference,
but if you have 100 light bulbs
and you turn one more light bulb on
it's such a tiny incremental difference.
So we're dealing with light
on this power function scale
where we're doubling and we're
halving, and so the value that gets us
to that middle gray is
actually 18% and not 50%
because it's not a linear scale.
Which there's plenty of math, and
I certainly won't do it justice,
but we can dive down that
rabbit hole another time.
So we looked a little bit
about what exposure is doing
and how we might fool
ourselves with the light meter,
but what are the actual settings that
I was just changing on the camera?
I was pushing and pulling
at some buttons and dials,
and I was clicking some things, and the
image was changing, but what was it?
So the three main camera controls.
The first one is ISO, which is the
sensitivity of a sensor to light,
or a film stock, or any kind of medium
that we're using to capture light.
The second is shutter speed.
How long do we let light strike
that sensitive medium for?
In the case of DSLRs it's
how long the shutter is open,
but maybe there are other
mechanisms in play on other cameras.
And the final one is aperture.
So in every lens there's a
diaphragm that opens and closes.
And depending on how open that
is or how small that is it
lets in more or less light.
That's a control that
we have at our disposal.
And so by using all
three of these elements
we can control how much light
reaches the photographic sensor,
and how sensitive that sensor
is to light more generally.
So let's dive in a little to each
of these categories because there
are different artifacts that happen when
we change and control each one of them.
So first one, ISO.
So it, again, measures the
sensitivity of a medium to light.
In digital cameras it's the sensor.
In old film cameras it's actually
a type of stock, like film stock,
and they each have different ISO values.
And the sensitivity
doubles and halves, which
is that unit of a stop, when the
ISO value is doubled or halved.
And in this little scale down below
there's some common ISO values.
A few of them you'll notice
are bigger than the other ones.
Those are-- maybe you can
call them major stops of ISO.
When you bought film
stock back in the day
it generally did not come in
these third stop increments.
It came as 100, or you'd
get 200, or 400, or 800.
So through that they've
become our major stops,
and there's ISO values in
between that digital cameras can
replicate at third stop intervals
or maybe half stop intervals.
But every time you double the number--
so if you go from 100 to 200
it's now twice as sensitive.
And if you half the number going from
800 to 400 it's half as sensitive.
And it works even with the third stops.
So say we had our camera
at 320 and we double it
to 640 that's doubling the
ISO value, that's one stop.
We've increased the exposure
value of the camera by one stop.
DAN: And by default most DSLRs that
you buy, and mirrorless as well,
will increment by thirds of a stop.
So you can set it to half
stop or only to do full stops,
but by default your camera
as you kind of click up--
and this is all the exposure values--
is a third of the stop.
IAN: Exactly.
So when we were shooting
on film predominantly
you would load a camera
with a roll of film,
and you would have one
ISO at your disposal
until you finished that roll of film.
So the flexibility of
digital cameras is sort of
amazing because in any given moment--
I had it on auto ISO by
accident, and it was just
sort of changing ISO to every stop
in between for any different shot
that we want to make.
So let's do a little
exercise 'cause I really
want to drive home this idea
of the relationality of stops.
So if we go from 200 ISO to 800 ISO
how many stops difference is that?
And is it more or less sensitive?
This is a good time for the internet
to chime in if you're on there
and want to join us.
Yeah?
AUDIENCE: I would say more sensitive.
IAN: It's more sensitive,
but how much more?
AUDIENCE: Two stops more sensitive.
IAN: Two stops because we to start at
200, and we go to 400, and then to 800.
So we've doubled, then doubled.
That's two stops difference.
Absolutely.
More sensitive.
Great.
How about this one?
Ooh, so much math.
All the arithmetic.
1,600 50.
How about someone from Zoom?
Anyone feeling brave?
DAN: Carla says five stops.
IAN: Five stops.
Yep.
Less sensitive.
Exactly.
Very good.
How about 320 to 400?
This is a little bit weird.
I was talking about it halving
in doubling, being a whole stop.
What do we think this might be?
One third up.
There we go.
Nice.
And then finally one where we have a
weird incremental stop that's maybe not
one of those major stops, 500 to 1,000.
Is it doubling or having?
Right, it's doubling.
It's going 500 to 1,000 It's
one more stop more sensitive.
This feels very basic in the
moment, but at the end of the day
having a firm grasp that when
you double and half you're
moving things in a stop increment it's
helpful because every other camera
control also moves in stop increments.
Can be controlled in stop increments.
So if you add a stop here you can
take a stop away somewhere else.
So because there is no
free lunch in anything
that we do and there are
nothing but trade-offs
there are artifacts that are
associated with different ISO values.
So increasing the sensitivity
of a medium introduces noise.
Does anyone have a sense of
what ISO noise looks like
or what noise is more generally?
Yeah.
So in the old days of film
it was actually grain.
You'd see particles that were actually--
the molecular structure of the film was
bigger so that it was more sensitive
to light because there was more surface
area.
In electronical-- or electronical--
[CHUCKLES]
In electronic systems it's
actually just random data
that gets introduced into our image.
And so the more
sensitive ISO values tend
to have much higher levels of noise.
And lower ISO values have less noise.
It's much more apparent in
the shadows of an image.
Why do you think that might be true?
Yes?
AUDIENCE: There's probably
less data in the shadows.
IAN: Yeah.
So there's less data in the shadows.
There's no information to
overwrite a noise value.
So you can see even low
value noise in shadows
because there's very
little data there to begin
with whereas if you have a lot
of-- like a bright highlight
it may overwrite sort of a
medium level value of noise.
The first place you're going to
see noise is always in the shadows.
So this is actually
from a cinema camera.
This is still of our
friend Dan Armendariz.
And here we can see him sitting in
this magnificent room at 400 ISO.
I don't see too much
wrong with this image.
I don't see a lot of noise anywhere.
It sort of seems fairly
clear and crisp to me.
At 3,200, well, I can sort of start
to see a little bit of degradation.
If we go back and then forward
there's some something there.
Still not crazy-- it doesn't
seem from this distance.
But then if we go to
12,800 that looks wild.
There's just so much
textural element to it.
So much noise.
And so it's a little
hard to see at that scale
so if we zoom in we have
Dan looking handsome.
Dan looking, ooh, a little horse.
And whoa.
And you definitely can see
it down in the shadow areas.
And I didn't mean to
make fun of Dan there.
He's a handsome man.
DAN: Ian, you we're talking about
the ISO levels like at 400--
IAN: Mm-hm.
DAN: I forget-- something
in the middle, and then
1,200, but is every camera the same?
IAN: No.
So every camera is not the same.
The range of ISO values that you have
available to you is hardware dependent.
So you'll find that certain cameras
can go from 50 to maybe 32,000.
Some of them have ludicrous numbers.
Like the A7S, I think, is
like 120,000 or something.
It can see in the dark.
Whereas a film camera
might be locked into one
ISO because you put
100 speed film in it.
Or maybe your camera only
has ISOs from 50 to 3,200.
And maybe it only has half
stop increments in between.
It doesn't have third stops.
So the range of ISOs that you have
available to you is hardware specific,
but the relationship is the
same regardless of hardware.
Doubling or having
increases or decreases
the sensitivity of the
medium by half or double.
DAN: And my question also--
like 400 on one camera, is it the
same as 400 on another camera?
IAN: I would say no because
at the end of the day
the way the hardware is interpreting
the electronic signals is
different for every single camera.
And so you may have one camera and
say, oh, there's no noise at 400 ISO,
and then use a different camera, and
you may find that in a specific image
there is a lot of noise at 400 ISO.
And so there is definite variability in
the quality of the electronic circuits
that are in digital cameras.
And so obviously higher
tier cameras are going
to do better at more ISO
values than lower tier cameras.
So, yeah.
DAN: So sensitivity-wise
they are the same,
but there are definitely trade
offs between different models
and different sensors as far as quality?
IAN: Right.
Exactly.
So has the same sensitivity,
but you may actually
end up with more noise,
more artifacts, and it's
because of the quality of the camera.
That's a good way to say it.
So why would you ever accept more noise?
Why would you why would
you increase the noise?
If it looks so bad why would you do it?
Well, it's a really pragmatic decision.
There sometimes is
just not enough light.
It's nighttime, it's dark, it's dusk.
There's just not a lot
of light and so you
need to boost up the
sensitivity of the sensor
to even render any kind of image.
So there's a very practical side of it.
Or maybe you're going
for aesthetic effect.
To mimic grainy footage.
Maybe you're trying to mimic some
surveillance footage or something
like that, or you want to go back to--
a lot of street photographers
used to shoot 3,200 speed film
and it always had really
heavy grain in it.
And maybe you like that
kind of look and style
and you want to add a
little bit of more noise
into your image to mimic that
for a textural effect, perhaps.
Here's a picture of a ghost I took.
I was ghost hunting last night.
Do you see it?
AUDIENCE: [INAUDIBLE]
IAN: All right.
Well, you guys will have
to investigate it later.
So shutter speed.
So that's ISO.
It's the sensitivity of the sensor.
Increasing the sensitivity
introduces noise.
Lowering the sensitivity
sort of minimizes noise,
but it also requires more light
so there's a trade off there.
So shutter speed.
So shutter speed is the amount of
time the sensor is exposed to light.
There is a shutter in here.
It opens for some period of time.
The sensor is struck by
light and then it closes.
We measure it in fractions
of a second, though you
may see them written on
cameras as integer values.
This is to save space.
On those tiny knobs
you may see like 1,000.
That's actually one over
1,000, 1/1000 of a second.
And listed there are the
major stops or shutter speeds.
This is what you would find on most
old school 35 millimeter film cameras.
Starting at a second and
going up to about 1/1000.
So, again, hardware specific.
Your camera may have more
shutter speeds available
to you, and in different increments.
Or it may have less.
But the important thing to take away
is that doubling the length of time
doubles the amount of light
that can strike the sensor.
Halving the length of time
halves the amount of light
that can strike the sensor.
So, again, we have this stop interval.
So you could imagine that if I have to
decrease the sensitivity of my sensor
maybe I can open the
shutter for twice as long.
So go down one stop here,
and up one stop here.
And it's the same amount of light just
manifesting a little bit differently.
So we're gonna count stops again.
So a 1/60 to a 1/15.
DAN: 1/60 of second.
IAN: 1/60 of a second.
I apologize.
I shorthand a lot of this,
but I should be more specific.
So 1/60 of a second to 1/15 of a second.
So it can be a little counter intuitive.
1/60 of a pizza is more or
less than 1/15 of a pizza?
That's how I have to do it
my head to be frank with you.
[CHUCKLES]
How many stops?
Yes?
AUDIENCE: Two stops.
IAN: Two stops.
So it goes from 1/60
to 1/30, 1/30 to 1/15.
Two stops more sensitive, or
more light striking the sensor.
1/1000 to 1/30?
So much counting.
DAN: Alex says five stop.
IAN: Bam.
Five stops.
And that's wrong.
That should say more sensitive.
That's a typo.
I apologize.
Because we're going from 1/1000
of a second to 1/30 of a second
that's much more light.
That should read five
stops more sensitive.
I'll fix that before
the end of the lecture.
So 1/500 to 1/400.
This is odd.
That doesn't feel like
a doubling or halving.
What might that be?
AUDIENCE: A third, maybe?
IAN: A third.
Yep, a third more sensitive.
And from 1/180 to 1/90?
Those are odd numbers that weren't
on our list, but it's still half.
Yep.
Exactly.
So it's one stop more.
So like all things that
we've talked about there
is a trade-off with shutter speed.
You can't just open up
your camera for as long
as you want and still expect
to render a crisp image.
So this is an image of a
dam that Dan took, and you
can see that the water is frozen.
It was falling down, and it's
literally frozen in midair.
So this must be a very
short shutter speed
in order to freeze motion like this.
The blink of an eye.
Here's the same image with
the same amount of light.
So technically these
exposures are equivalent,
but they look very different.
In this one there's time for the water
to fall all the way down and create
this sort of streaking
effect in the image.
So this is a slower shutter speed.
What is it?
Half a second.
So the shutter is open
for half a second,
whereas in the previous one what was it?
1/4000 of a second.
That's beyond fathoming to me.
It's a little too fast.
And so this image
takes a second to load,
but you can see here a
composite image that Dan's made
that starts at very slow shutter speeds,
and moves towards very fast shutter
speeds.
And if we actually put
the shutter speeds there
you can see incrementally
where motion begins
to look how we might
perceive it normally
into being frozen
instantaneously or drifting
into this fairy-like wishy-ness.
DAN: This kind of raises the question
of how fast is fast enough too?
So it really depends on your subject.
For sports maybe one 1/250 of a second
is fast enough to freeze motion,
but obviously to freeze waterfall you
need to crank it up even further, so.
IAN: Yeah.
DAN: So it depends.
IAN: And also perception
too because when
I think about when I turn my tap on, and
what I see I see something over here.
I can't make out individual
drops unless I'm tracking them.
It's gushing, but it
doesn't look like this.
This is sort of very ethereal.
And it definitely doesn't look
frozen in time like the one
before so the speed
of the object matters.
And sort of our perception
of that speed as humans
defines how what it
looks naturalistically.
AUDIENCE: That's to say human eyes
are sort of equivalent to some f-stop,
would you say?
IAN: I don't know.
Maybe--
DAN: There are arguments
online that yes, but--
IAN: Oh, I'm going back.
DAN: I think It varies very much
by person to person as well.
IAN: Yeah.
And I think the argument is you
have to be looking at a fixed point.
And everything-- when
humans track objects--
fast moving objects to achieve
more clarity than maybe
if something passes right
in front of your vision
while you look at a fixed point.
So it's a really hard
experiment to perform
because people eyes are always moving.
And if you move something in front
of them they just will track it.
And you sort of get--
it's all skewed data I would say.
But there probably is
some sort of upper bound
of what we can resolve with our eyes.
Just as fast as they refresh.
So this is last night's snowy night.
Snow is just streaking
down through these wires.
Here's another one with a tree.
DAN: Just to go back one second
to the previous conversation.
I think it also largely
comes down to something
known as frame rate, which is how
many images you see in sequence,
and what human perception is to believe
something is actually in motion.
And so I think that is a
bigger part than shutter speed,
for example, as far as what
feels natural and feels normal.
And we're going to punt to
the next lecture in here
on that when we talk about video.
IAN: Yeah.
It's sort of the idea of
persistence of vision.
Video is not moving images.
It's a sequence of still
images, and we perceive them
as moving because they happen
fast enough that we don't notice.
So there is some sort of
threshold where that happens.
I'm just not convinced
I know what it is.
So to sort of jump
back to that idea of we
can actually track objects to
increase the perceptive focus of this,
this is a car that's driving
by, but by panning with the car
I was able to capture this in focus
while the rest of it is out of focus
at a much slower shutter speed.
If I hadn't moved the camera at
all everything would be blurred.
It would just be a large streak.
DAN: And I think we should
be careful with what you say
is in focus versus what's not in focus.
This is actually motion blur,
which is different from something
being in soft focus.
IAN: That is true.
A very important distinction.
So this is actually--
as it moves across the sensor
it ends up looking blurry,
which is the idea of that
motion blur for sure.
So it does lead us to this question
that if shutter speeds get low enough
you can actually introduce shake or
movement just from your own human body.
This camera's on a tripod.
It's very stable, but if I hold
something I'm always moving.
Always.
Try as hard as I might.
So the rule of thumb is to minimize
hand-held camera shake set your shutter
speed to faster than one
over your focal length.
So it seems confusing, but I have
a 50 millimeter lens on here.
In order for there not to be any
camera shake when I hand hold it
I should be shooting it
faster than 1/50 of a second.
If I put a 70 millimeter lens on here
or a 100 millimeter lens then maybe
I want to shoot at 1/70 or 1/100.
So, especially-- this comes into play
a little bit more too with zoom lenses
where you might be zooming in and
out and changing your focal length,
and not sort of paying attention
to what shutter speed you're at.
And you're say at 1/70 of second and
you're shooting at 70 millimeters,
but then you sort of snap
into 200 all of a sudden
you're going to introduce
camera shake into the image.
A little bit of motion blur that
reduces the crispness of your images.
So aperture.
The final of our three is the
size of the opening in a lens.
And we have a little short
video to tease you with this
if we can just watch like this.
So as the lens gets more and more
open what do you notice happening?
AUDIENCE: The numbers get smaller.
IAN: Yeah, the numbers get smaller.
This is odd.
Interesting.
So aperture actually refers to the size
of the diaphragm opening in a lens.
And it's a fractional relationship
between the size of the opening
and the length of the lens.
So it, again, is
written in the integer--
as integers or decimals on camera
bodies and lenses and things like that,
but it's actually like
a fractional amount.
So it's 1/2 or 1/2.8.
So 1/22 is smaller than one half.
And that's why the
diameter of the opening
gets smaller the larger the number gets.
It's a little frustrating,
and counter intuitive,
and can be confusing, if
you're not used to this,
but with practice I
promise you'll grab it.
So the major f-stops are
listed below up to 22.
You can have smaller apertures
like f/32, or 45, or 64.
And there are increments in between.
There are third stop
increments in between.
You may find someone that shoots
something at f/9 or something like that
and you're like, well,
that's not listed here,
but so there's increments in between.
And just to drive home the point
that the smaller the f number
is the larger the opening.
So over here we're in like 2.8,
and over there we're at f/22.
And so when you refer to
the size of an aperture
you might just say F
whatever the number value.
So I'm at f/2, or I'm at
f/16, or f/8 to denote
that you're talking about
the size of the aperture,
and not some other numerical value
associated with camera exposure.
So artifacts of aperture.
Again, there are
trade-offs with everything.
So changing the aperture directly
affects the depth of field of an image.
We have not talked about
depth of field except sort
of in glancing blows in critique.
And depth of field is defined as the
amount of an image in apparent focus.
So in reality with the
way optics are there's
only one single plane of
critical focus in an image
that runs perpendicular
to the lens axis.
And it's set at some
distance from the lens.
And if you look at your
lens you'll probably
see that there's feet and
meter indicators on there.
And when you adjust
those to a witness mark
that's how far away that
critical plane of focus is.
But, before we get there,
that's sort of obviously not
how we experience photographs.
We often look at
photographs where there's
more things in focus on the
z-axis than a single plane.
So there's some artifact
that's happening
when cameras make images that
allow us to have more in focus
than just a single plane, and
that is what depth of field is.
How much distance on the
z-axis is in apparent focus.
And we'll come all the
way back around to depth
of field in just a few
minutes, but that's
the concept that we're talking about,
and aperture directly affects it.
Oops.
Forward.
So here we have an image
of a young man in--
DAN: Handsome young man.
IAN: What?
DAN: A handsome young man.
IAN: Handsome young man in a swing.
And I used Dan's son as my stand in.
But you'll notice that the back
of the image is out of focus.
And so we're at what?
At f/1.4.
So in this image-- which
is a really large opening--
really large aperture opening.
If we go one more image we're now at
11 so the aperture has gotten smaller.
And we've compensated for that
with other exposure controls,
but now you can see that all
of this background is in focus.
I love that he sort of looks
over his shoulder at that point.
What's that?
And so side by side you can see that
these images while the exposure is
the same, the brightness
of the light values
and the darkness of the dark values
is the same, they look very different.
And so you can use depth of
field as a creative tool.
And it's often used to separate
people from environments
to make things more intimate, or to
show how expansive an environment might
be if you go the other way.
DAN: Can I--
IAN: Yeah.
DAN: [? Can ?] I give an easy
way to remember the f-stops?
IAN: Yeah.
DAN: Can you set a drawing for me?
IAN: Yeah, I can.
DAN: So I to this day I have
trouble remembering these numbers,
just like-- you know, you
get to know the majors,
but the easiest way for me to
visualize this as you're going along
is start with one and 1.4.
And so the nice thing now is you can
just keep doubling along the way.
So one you double to two.
1.4 doubles to 2.8.
Two doubles to four.
2.8 doubles to 5.6.
Four doubles to eight.
5.6 doubles to approximately 11.
We round here.
Eight doubles to 16.
11 doubles to 22.
And that covers most lenses that
you'll pick up and operate with.
So if you're trying to remember this
scale just remember one and 1.4,
and then keep doubling.
IAN: Quick and dirty.
So we talked-- oops.
So I was alluding to--
these have the same--
they're allowing the same amount
of light to strike the sensor.
They're just using different
settings in order to do this.
So that means that
there's some sort of idea
that you can have different
exposure settings that
yield equivalently exposed
images with different artifacts.
And so as a photographer,
or an image maker,
you have to make decisions about which
artifacts you want and which ones you
don't.
And it comes back to that idea that we
were talking about so much of intention
and supporting your narrative story.
'Cause this image over here is
very much about this young boy.
And this image is actually about
this boy in a larger environment.
And by making the decision to
have narrow depth of field we're
focused in with the child, but
to have expensive depth of field
we're sort of looking at the child
in relationship to the space.
So exposure equivalencies.
So we can expose the same
scene with different settings,
and yield an image that is at exposure.
But how does the image change?
So to come back to this image
again, this is exposed at ISO 100.
So a lot of noise?
Not a lot of noise in that do you think?
AUDIENCE: Low.
IAN: So low noise probably.
It's at f/5.6.
So is that a lot of depth of
field or a little depth of field?
Shallow or narrow?
AUDIENCE: In the middle.
IAN: It's in the
middle-ish we could say.
And it's exposed at 1/100 of a second.
So when we think back to the image of
the dam with all the sequential shutter
speeds on that it's not super
fast right to freeze anything
like falling water or anything
moving really fast, but fast enough
to freeze most things.
And it's also not slow enough to
allow significant motion blur.
So here's the same image, and
we've changed a couple of things.
We're now shooting at ISO 400.
So what have we done
compared to the last image?
AUDIENCE: Doubled the ISO?
IAN: We were at 100 before
so we went 100 to 200.
200 to 400.
So we increased the
sensitivity by two stops,
but we also opened up the
aperture by several stops,
and then shrank the shutter
speed by a fair amount.
But what you'll see is that f/1.4 is
a really big opening and has a very
shallow depth of field.
And you can begin to see that.
If we go backwards you
can see detail here.
Crispness.
We go forward and it's totally blurry.
And we know that that's
probably not motion blur
because we're shooting at 1/6400 of
a second, which is incredibly fast.
It's fast enough to freeze
water and most anything
that we would deal
with in our daily life.
So here's another version of this image.
We're still shooting at a
very high shutter speed.
We're shooting at a deeper--
or a smaller aperture, which
gives us deeper depth of field,
but we're shooting at this
really wildly high ISO, which
introduces a lot of noise.
And it's difficult to see, but we'll
zoom in on this in just a second.
So again, just to go the other way.
So we have f/1.4.
And this is 1/8000 of a second, which--
there's not a lot moving in here,
but there's relatively no motion blur.
DAN: There would be nothing
moving even if there were.
IAN: Yeah.
Exactly, but it wouldn't
be moving if it was.
And a sort of relatively benign ISO 640.
And again f/22.
And we notice that the difference
between f/1.4 if you look at that
gravestone in the very
far background there.
This guy here.
All of a sudden--
oops, I went the wrong way--
at f/22 it's sort of crisp,
whereas before it was out of focus.
DAN: And, Ian, you said a
moment ago a benign ISO here,
but I don't know that you defined
what is an acceptable ISO range?
Like we talked about the trade
of a high ISO introducing noise,
and a low ISO having less
noise, but like in your-- maybe
this is an experiential question.
In your experience--
IAN: Yeah
DAN: --like what would
your target range be
if you're going to go
out and shoot something
and wanted to keep as little noise as
possible while giving yourself a range,
what would you operate in?
IAN: So I tend to shoot
between 100 and 400.
And I think that may be just habit
from shooting 35 millimeter film
where I would buy it at 100
speed, or 200 speed, or 400 speed,
but mostly 100 and 400.
But I think on any given
shot I'm willing to push up
to like 800, maybe 1,000, and once
I get past that it just starts to--
I need to really want
to have the grain there
because it gets hard to get rid of.
So I would say experientially,
yeah, I shoot around 400.
400 to 800 is sort of what I shoot
because it's sensitive enough
that I can be in a reasonably dark
situation and capture what I want,
but it's also just not
introducing that much noise
that there's a real problem when I
go in and look at the images later.
Yeah?
AUDIENCE: Are you shooting
full frame or crop?
IAN: Full frame.
Well, it depends.
It depends which camera I'm using.
So I'll shoot full frame, which
means a 35 millimeter size sensor,
but I own cameras that have
smaller sensors than that.
And so the-- yeah, and so
and so it really depends
on what piece of hardware I'm using.
Again, all of these values and
things are dependent on the hardware
that you have.
DAN: Yeah, but I think Ralph's
question is actually interesting
asking which size sensor.
Is there a performance difference with
a bigger sensor versus a smaller sensor?
IAN: Yeah, there is because you
can have larger photo sites.
So because you have a larger sensor the
photosites that are sensitive to light
can be larger which means
that they are effectively
better at higher sensitivities than
sensors that have smaller photosites.
So a full frame or a
larger sensor is going
to have better quality in
lower light than something
that has a smaller photo sensor.
DAN: With a higher ISO.
IAN: Yeah, with a higher ISO.
I think, all things
being equal, if you say
have like a small micro 4/3
mirrorless camera at ISO 400
they're probably indistinguishable.
Maybe if you really, really, really
dig into the image you can find it.
But if you're shooting it say 3,200,
or 6,400, or something like that,
having a larger photosite,
which means a bigger sensor,
is going to be more beneficial to you.
That's where you're going to find that
little bit of edge that it gives you.
For sure.
It's a good question.
DAN: And then I just want to highlight--
Alec said that there's
vignetting on the lens.
It's very noticeable between 1.4 f/11.
IAN: Yeah, there definitely is.
AUDIENCE: There is.
IAN: Yeah, like you can see it here.
At 22 all the corners
are bright, and at 1.4
for there's this serious vignetting.
And it almost feels like it's
softening too a little bit.
And what that is is that
the coverage of the lens
is sort of just getting a little
bit too small for the sensor size
and it's just-- not quite enough light
is reaching the sensor at that time.
So I'm going the wrong way.
That's why they keep going.
So if we jump in and look at both.
This is the first image, which was
sort of medium values of everything.
It's very vanilla.
This is 1.4 and you can
see my focus was just off.
AUDIENCE: It's hard to focus at 1.4.
IAN: It's really hard.
And I sort of left this
in here as an illustration
that you might think you have
something in focus when you're
looking at it with a
smaller aperture, but then
if you open up it may not quite be--
you're plane of focus might not be
exactly where you expected it to be.
And this is very--
like this happens a lot.
Like it's not far off really.
It's on this bush here somewhere,
but it's just too far forward.
Like I made a mistake.
DAN: And it's really unfortunate when
you're shooting with a person and--
IAN: Yeah.
DAN: The thing you want when you're
shooting a person is for their eyes
to be in focus because that's like the
first thing your eyes typically go to.
And when you perceive an image in
focus the eyes are typically in focus.
So if you notice that the focus is
like just on the end of someone's nose,
but their eyes are not in focus it's
definitely a moment to kind of-- it's
good to double check if you're
taking a picture of people,
I guess, to punch in
digitally on your screen
and make sure that the
image is actually sharp.
So
IAN: This is that image
with a really high ISO.
And I think it was a little
bit difficult to see,
but in when we zoom
in now you really can
see the noise just sort of
introduced and all of the texture.
And you'll almost see-- like
it's almost a little bit brighter
too because there's so much
added bright data in the shadows.
Lift them up a little bit
because there's so much of it.
So, again, 1.4 again was my bad focus.
So frustrating.
AUDIENCE: It happens to all of us.
IAN: Right.
But then if we go to f/22--
and this is what tricked me because I
think I actually shot this one first
and I was like, ah, it's in focus.
Looks great.
You can see that this
background is in focus.
And this foreground object is in focus.
So it has a large depth of field.
So this should visually
illustrate that we
have the ability to have different
exposure settings for the same exposure
value.
So if we think about a
scene in this way there
is some sort of amount of available
light that we want to sort of render.
And we have three controls
at our disposal to do that.
And by increasing or decreasing
one we can increase or decrease
the overall sensitivity of the
camera to some amount of light.
Or we can increase one and
decrease another to not change
the sensitivity of the camera, but
the change the way that image looks.
So if we think about this-- if we assume
that are base exposure that we metered
returned some values like f/5.6, 400
ISO at 1/60 a second, which is, again,
not that grainy.
It's not that fast.
Not that slow.
There's not a lot of
room for motion blur.
Someone walking would be fine.
A car might be out of--
a moving car might have
a little blur to it.
Someone standing still would be fine.
And the depth of field
is in the middle range.
We haven't figured out quite what
that means, how much that means,
but we know it's in the
middle compared to 1.4 or 22.
So let's make some decisions.
Let's change the way this image looks.
And what I've done is I've
filled in two of the three blanks
with different numbers.
So we should at this point be able
to calculate what the empty is.
So we'll just walk through
the very first one.
So before we were at 5.6 and then
we closed down one stop to f/8
so we allow less light in by one stop.
Here we're at 400.
We're still at 400.
So we've allowed one stop less light in.
So now we need to compensate for that.
And we're going to compensate
for that in this empty square.
So we need to allow one stop more
light in to make them equivalent.
Does it make sense?
So what would the value
be in that square?
Yeah?
AUDIENCE: [INAUDIBLE]
DAN: I've got the internet.
You're right here.
Go ahead.
AUDIENCE: Yeah, but [INAUDIBLE].
I haven't heard them all day.
DAN: Miles says should we
go up to 1/30 of a second?
IAN: We should.
Well done.
That's awesome.
So we reduce the amount of light by
one stop by closing the aperture down.
So we had to increase the amount
of time that the shutter speed
was open by one stop.
This isn't the only decision we could
have made, but it is the decision here.
AUDIENCE: For the
proper exposure, right?
IAN: Yeah, to maintain our exposure.
The same exposure that we had given
by these yellow numbers up here.
So now we have a
different set of numbers.
And again, we're still going to
reference the yellow numbers.
Don't worry about the bottom one.
So we open up the
camera from 5.6 to 1.4.
DAN: Can you go back to my drawing?
IAN: Yeah.
DAN: To go this far I
still have to visualize it.
So we're going from 1.4--
IAN: Well, we started at 5.6.
DAN: Right, sorry.
IAN: Was the original
exposure value, and we're
going to open up the aperture to 1.4.
DAN: 1, 2, 3.
IAN: 4.
DAN: I won't say the final number.
Somebody else can say it.
IAN: So we've added four stops more
light by adjusting the aperture value.
We still haven't adjusted the
ISO value so that's the same.
So we now just have to compensate
for four stops more light.
Got a few answers from online.
AUDIENCE: Do you need
more light or less light?
IAN: Well, so you tell me.
We started at 5.6 and
we're going to 1.4.
AUDIENCE: OK.
We need to add more.
OK, yeah, I'm good.
I'm good.
IAN: Right.
So the smaller numbers
are larger openings,
which is sort of counter intuitive,
but we've gone five stops more open.
So where would the shutter speed go to?
You said you have an answer?
DAN: I have a few answers from online.
IAN: OK.
DAN: So I have 1/240.
I've got 1/1000.
1/960.
IAN: OK.
So we'll start with the lowest
and we'll go all the way up.
So 1/240.
So we were at 1/60 and we want to
reduce the amount by four stops, right?
Is that what we decided?
So we go 160 to 120.
1/120 to 1/250, which
doesn't match perfectly,
but that's sort of the way it is.
1/250 to 1/500, and 1/500 500 to 1/1000.
That's our four stops.
So we end up at 1/1000 of a second.
DAN: And this is a good moment to
highlight the rounding that we do.
The kind of fudging of the math.
It's the same thing from 5.6
to f/11 when we make that jump.
It's not quite, but it's
easier to talk in whole numbers
than it is to remember
1/960 of a second.
IAN: Right, exactly.
And so you will find as you
investigate some of these concepts
that some of the numbers
are scales on the cameras.
Maybe you do have that fudge
factor when you go from 5.6 to 11,
which doesn't quite make sense.
Which should be 11.2 I think.
All right, so let's do this one here.
So we're at 5.6, and we open up to 2.8.
How many stops?
AUDIENCE: Two stops?
IAN: 5.6, four, 2.8.
Yeah, two stops.
1/60 to 1/30.
Opening or closing?
More sensitive or less sensitive?
AUDIENCE: More.
IAN: More sensitive.
By how many stops?
AUDIENCE: One.
IAN: One.
So we add one more.
So that's three stops difference.
So now if we were at ISO 400 and
we've added three stops of light
how much less sensitive
do we need to make that?
There's so much arithmetic.
It's annoying, I know.
But I'll make you really good at it.
AUDIENCE: Three stops.
IAN: Yeah, so we need
to go down three stops.
So what is the numerical value for that?
AUDIENCE: [INAUDIBLE]
IAN: OK, perfect.
That's exactly right.
Great.
AUDIENCE: [INAUDIBLE]
IAN: Great.
All right, so our last
one we've doubled the ISO.
We've done something
with the shutter speed.
How many stops differences is
the shutter speed from 1/60?
Oh, I still have to do it my head.
1/30.
1/15.
So you go from 1/60 to 1/30,
1/30 to 1/15, 1/15 to 1/8.
That doesn't make any sense,
but that's what the number is.
So it's three stops more light.
And we've also doubled the ISO.
So that's one stop more sensitivity.
So that's a total of four stops.
So if we take the aperture we need
to close down four stops from 5.6
so we just go the other way.
We go 5.6 to eight, eight
to 11, 11 to 16, 16 to 22--
f/22.
And finally this last one.
I don't even understand this one.
We'll go 400 to 320.
That is not halving nor doubling.
What do we do?
AUDIENCE: It's a third isn't it?
IAN: Yeah.
Let's do the rough math.
It's about a third.
So I've got a third of a stop.
I don't know how to do
that with my fingers
so I'll just keep it in my head.
Now we go from 1/60 to 1/100.
Is that a full stop?
Full stop would be 1/120.
So it's 2/3.
So now we have 2/3 and 1/3.
Ah, one stop.
AUDIENCE: [INAUDIBLE] can handle that.
IAN: Perfect.
So we just have to open up to f/4.
So it can get a little funky.
And it can get-- like you can start to
sort of move and shake things around,
but you literally can
make different images.
So what does this image look?
This middle one?
1.4, 400, 1/1000 of a second?
AUDIENCE: There would be a vignette.
IAN: Yeah.
So we noticed that when it was at
1.4 with this lens on this camera
there was seriously vignetting so
if we use this same system again
we'll get serious vignetting,
but what's the artifact
that we'll really care about?
AUDIENCE: [INAUDIBLE] a
shallow depth of field.
IAN: It'll have very
shallow depth of field.
What about things that
are moving in that?
Say there's some cars in it.
AUDIENCE: They'll be frozen.
IAN: Yeah, they're going to be frozen.
1/1000 of a second.
That's pretty fast.
That's 1,000 pictures in one second.
That's actually pretty ludicrously
fast if I think about it.
So very shallow depth of
field, but no motion blur.
So blur because of depth of field--
or lack of focus because of the depth
a field, but what about this one?
F/22 at 800 at 1/8 of a second?
Yeah?
AUDIENCE: You'll have wide
depth-- very wide depth of field.
IAN: Mm-hm.
AUDIENCE: And potentially,
depending on the lens,
it's gonna have like a
bit of shake or blur.
IAN: Mm-hm.
AUDIENCE: At 800 I'm
assuming not too bad.
Not too much grain.
IAN: Yeah, but more than 400 for sure.
So large depth of field
and then some motion blur.
1/8 of a second.
I can do a lot in 1/8 of a second.
Like I moved.
A lot of dancing in 1/8 of a second.
So that is to say that
we can actually speculate
at what these images
look like abstractly just
by looking at the camera settings.
We have an understanding of how
to previsualize what a scene will
look like at given settings.
So when you're out photographing you
can look at a scene and you can be like,
oh, so there's cars moving,
there's some water flowing,
I know if I set a low shutter speed
I'm going to get interesting blur.
Cool, I want to try that.
And you know that you can
then decrease the shutter
speed so that you end
up with more light,
and then you maybe have to stop down.
It's going to increase
your depth of field,
which may be an interesting image.
Now I'm going backwards again.
So briefly, what do you think the
camera settings were for this image?
And we're going to talk abstractly
without sort of like digging
into the image file.
We don't know for sure, but
we can take some guesses.
AUDIENCE: F/11.
IAN: OK, so you're saying f/11,
but why are you saying that?
AUDIENCE: Well, a lot's in focus.
IAN: So there's a large depth field.
That's our first
indicator, so we're going
to say that it's probably
a small aperture.
F/11, maybe higher.
Who knows?
But like a small aperture for sure.
What about the shutter speed?
AUDIENCE: Relatively slow.
IAN: Relatively slow.
Why do you say that?
AUDIENCE: [INAUDIBLE] shutter speed,
there would be a shadow on that,
I guess.
IAN: Well, we don't we don't know
how much light was at the scene.
We don't know, but what we can
do is look at the artifacts.
And the artifact of shutter
speed is is there motion blur?
Is there not?
Is there motion blur on certain
things and not other things?
Because that gives us an
indication of how fast it is.
AUDIENCE: It doesn't look like there's
much motion [INAUDIBLE] at all.
IAN: Yeah, so I think--
you know, where there's--
the water is rippling in some wind
and that seems relatively crisp.
Like maybe there's a little bit of
motion blur there, but it's not a lot.
It's not sort of
distracting, and it doesn't
look like the water in the dam picture,
which was super smooth and flowing.
AUDIENCE: Carla says 600 ISO.
IAN: 600 ISO.
AUDIENCE: What?
IAN: Yeah, why?
So why?
AUDIENCE: [INAUDIBLE] be more.
IAN: What is the reasoning for that?
The logic behind that assessment?
AUDIENCE: Aperture's closed down.
IAN: I don't see a lot of grain so if
that is the idea-- like, yeah, there's
not a lot of noise.
And so I think we could say
that this scene probably
has a fair amount of light in it.
It's a sunlit vista.
And there's a reasonably high shutter
speed, a large depth of field,
and some relatively low ISO.
AUDIENCE: Yeah.
IAN: Right?
And maybe-- yes?
AUDIENCE: Isn't another artifact of
a low ISO good color reproduction?
'Cause like when I saw the picture at
the beginning with-- what's his name?
I don't know if his
name was Dan as well.
Was his name Dan [INAUDIBLE]?
IAN: Mm-hm.
AUDIENCE: So like at 400
the colors looked OK,
but when you went to 1,200,
800, it was blotchy and colors
that weren't there started to exist.
IAN: Yeah, so in that sense
because noise is random
and it's not just
brightness values, it's
also color values, that you
can get random red introduced
at a pixel or a bunch of
other pixels and so the color
loses fidelity with the introduction
of noise in the same way
that your exposure loses fidelity.
And you notice in the graveyard
image where it seemed almost brighter
because there was so much
noise in the shadow it easily
could have been like seemed more
colorful or the colors seemed
off and messed up because of like
random color data forming as noise.
So, yes, in that sense absolutely.
DAN: Yeah, and with the stretching
of the information basically
you're sensor's just like stretching the
information that it is able to collect.
As we saw there was a lot--
when the noise comes up in
the shadows that can also
lead to the perception
of lack of contrast
as well because there's just like
more noise across the darks that
seem to raise them
more than they actually
are so there's better reproduction at
a lower ISO because of that as well.
IAN: So what's going on in this image?
Hm?
AUDIENCE: Looks like a California.
IAN: Maybe.
Are they cormorants or pelicans?
I don't know.
High ISO or low ISO?
We'll start there.
DAN: Getting a lot of slow shutters.
Long shutter--
IAN: Yeah.
I think the most the most sort of
dramatic thing about this image
is the slow shutter speed
that allows the water to blur.
And the depth of field is--
I don't know.
I mean there's some
definition in the water out
in the far horizon and the rock so maybe
it's pretty large, but it's, you know--
and I don't notice a lot of noise so.
But the most dramatic
feature of this is someone
is utilizing a slow shutter speed for
an interesting compositional effect.
AUDIENCE: And I would say it's
low noise because when you
have the sun that's a powerful source.
IAN: Yeah, right.
So they may not need
a lot of sensitivity,
but we don't know what time of year?
What time of day?
This could be evening or early morning
so there's a lot of room for variation.
Our error bars are large with
that's that sort of idea,
but yep the sun is an incredibly
strong source of illumination
so probably not something
really, really high.
And we also don't see
any artifacts of that.
I don't see a lot of noise in the image.
How about this one?
AUDIENCE: Very small f-stop.
IAN: Yeah.
So a very small f-stop.
Well, actually I think we should
say a small aperture opening, which
is a large f-stop number.
Just to be specific because it gets
so confusing otherwise if you're like,
oh, it's a large f-stop
and you're like, but is
that the big number or the big opening?
So.
AUDIENCE: Small number, big opening.
IAN: Yeah, yeah.
No, but just-- it takes
muscle memory and practice.
So this is really about sort of diving
into a very small section of an image
and letting the out of focus play is
sort of a graphic element around that.
There doesn't appear
to be a lot of noise,
and there's not a lot to
suggest anything either way
about the shutter speed.
It's some sort of neutral value, but
they made a very conscious choice
to shoot at a very large aperture
to get a shallow depth of field.
Whoa.
What's this one?
DAN: Fast shutter
speed, [INAUDIBLE] says.
IAN: Yep, exactly.
And not much to suggest--
I mean, the depth the field
feels pretty reasonable.
I can see things in the
background that are in focus.
The water is completely
stopped midair for sure.
AUDIENCE: It's a big aperture.
IAN: Yeah, yeah, yeah.
Absolutely.
Whoa.
God.
What about this one?
AUDIENCE: High ISO.
IAN: Yeah.
I would agree.
Absolutely.
That's a good read.
AUDIENCE: [INAUDIBLE]. fast ISO.
IAN: Yeah.
What about the shutter speed though too?
This is sort of interesting.
AUDIENCE: Yeah.
I would say fast 'cause look,
they're frozen in the air.
IAN: Yeah, they're frozen in
midair so it's fast enough
to stop someone in mid leap.
But also they see in
order to do that they
needed to boost up the ISO to make it
more sensitive because it was allowing
such little light in for the time.
AUDIENCE: Yeah, and there's a
lot in focus in the picture.
IAN: Yeah.
AUDIENCE: How did they get this picture?
IAN: By boosting the ISO.
And I think you could-- like
the level of grain in the image,
or noise in the image,
is really apparent.
AUDIENCE: Yes.
IAN: Yeah?
AUDIENCE: One thing
on this image as well,
like you mentioned about color
reproduction and higher ISO.
IAN: Mm-hm.
AUDIENCE: I think this image
might be made black and white
and that's one kind of
thing people sometimes
do when they bump up their ISOs.
When you have bad color you just
make it black and white [INAUDIBLE]..
IAN: Yeah, because the color
gets really mushy and noisy,
and then the black and
white begins to feel
like a textural
compositional element rather
than a degradation of some other image.
That's a very good point.
Nope.
Backwards again.
So let's take a five minute break
at 7:04, and then we'll come back
and we'll talk a little
bit about depth of field
because I've sort of been saying
oh there's large depth of field
and shallow depth of field,
but we don't know what it is.
So let's demystify this when we
return in just a couple of minutes.
All right, folks.
Welcome back.
So We're gonna dive right in and
start talking a little bit about depth
of field as a creative tool, and
also how it works from a functional
standpoint with your camera.
So depth of field is the amount of
any image that's in apparent focus.
We've seen some images where there's
only-- a tiny part of the frame
is in focus and everything
else is sort of blurring out
in the foreground and the background.
And we've seen images where
everything from the foreground
object to the vast horizon
in the distance is in focus.
So we need to be careful because
apparent focus is the linchpin of this.
There is only one plane
of focus in an image,
and it's set when you adjust
the focal ring on your lens
and choose some distance
at that witness mark.
The rest of everything that you perceive
as in focus is apparently sharp.
It's sharp enough that our human eyes
don't notice that it's out of focus.
So there is a threshold
where at a certain point
our eyes do notice
that it's out of focus.
And this threshold is much
lower on smaller images.
And as you blow things
up, and I think you
may have experienced this,
where you take a picture
and it feels like it's sharp,
like my gravestone image.
And then I blow it up to
a big size and I'm like,
oh, it's actually out of focus.
AUDIENCE: [INAUDIBLE]
IAN: Yeah, on an 85 inch TV.
So there is this relationship to how
that apparent level of focus breaking
down the larger you enlarge an image.
So the bigger print that
you're going to make,
the larger you're going to project
something, the more important
it is to make sure that you nail
that critical plane of focus.
And to Dan's point we often,
when we're doing portraiture,
put that right through the eyes.
So that we know that this
person's perfectly in focus,
and that as the depth
of field grows we'll get
a wonderful image of their whole face.
So what does this look
like more generally?
So this is a funky
diagram that I made where
you have this sensor plane that's
inside of the camera, you have a lens,
and then you have your plane of
focus out here set to some distance.
So one of the interesting
things about depth of field
is that it's not perfectly 50/50
surrounding that plane of focus.
So the amount that's apparently in
focus is 1/3 third in front of it
and 2/3 behind it.
So there's actually a little more
behind that plane of focus that
appears in focus than in front of it.
And this is a handy
trick if you're really
shallow, you have a really
shallow depth of field,
you can actually cheat that plane
of focus a little bit forward
to make use of that extra
space that's behind it.
Nope.
I keep-- do I keep going backwards?
So we described depth of
field as being deep when
there's much of an
image in apparent focus,
and conversely when only a
small area is in apparent focus
we describe that as being shallow.
The three factors that control this
are our aperture, focal length,
and the focusing distance of the lens.
So the only exposure control that
effects depth of field is aperture,
but other elements effect
depth of field as well.
And that means the length of the
lens, whether you're at a wide,
normal, or tele.
And how closely the lens is focused.
Whether you're focused
at a subject really,
really close in front of the
lens or much, much further away.
So to sort of talk a little
bit more concretely about this.
So the smaller the opening the deeper
the depth of field for aperture.
So f/22 will make a deeper depth the
field in the same image than f/1.4.
And we saw some examples of that with
the cemetery shot where there's--
the background gravestone was out
of focus, but then it was in focus.
The larger the opening the
shallower the depth the field.
And there's this little basic--
major stops down there.
Shallow are going this way towards
more open and the smaller F number.
And deeper going towards the larger
F number but smaller opening.
So your rule of thumb to
help you make sense of this
is that doubling the aperture
doubles the depth field.
Yes?
AUDIENCE: [INAUDIBLE]
IAN: So it's a little bit helpful that
if you don't have enough depth of field
you can double the amount of it
just by opening up one stop--
or closing down one stop.
I'm sorry.
Closing down one stop and
adjusting one of the other exposure
controls to give you a little
bit more depth of field.
So a big thank you to Andrew Markham
for sitting in for us on this.
But what we have here
is a wide angle lens
set to f/16 with some amount
of lighting in a space.
And what I want to look at is not just
our subject, but the area behind them.
And watch what happens
as we play this video.
So what we're actually
doing in this moment
is opening up the aperture at
the same time as we decrease
the amount of light in the space.
So we're actually dimming the
lights as we open up the aperture.
And what you see is in the
starting frame when we're at f/16
all this appears crisp.
Maybe a little blurry, but much
crisper than this, for certain.
So this is a wide angle lens.
Do you remember what focal
length we were at, Dan?
25, let's say.
Maybe.
DAN: There was crop factor there too.
IAN: Yeah, yeah, yeah.
But it definitely is a wide angle lens.
And then if we look at this same
situation with a normal lens
we'll see something interesting happen.
Remember that I said that focal
length increases depth of field.
So here we are with a normal lens.
The angle of view has shrank a bit.
The camera hasn't moved.
We've just tightened
up the lens a little.
Remember from Dan's lecture.
And we'll do the same thing
again where we start at f/16
and we'll open up the aperture.
And we'll actually just sort
of dim the lights in concert.
And if we look at this one, again, you
see that the background is in focus.
And then it's out of focus,
but is it more out of focus
than the previous one?
AUDIENCE: Yes.
IAN: OK.
Yeah.
That's sort of interesting.
So now we'll move to a telephoto lens.
Again, the angle of view
cropping in-- or not cropping in,
but we'll run this again.
And now it's really soft.
Incredibly soft.
And this is the difference between them.
And I would say that this starting
softness out here is not quite as crisp
as it was in the earlier two iterations
of this, but that is much much softer.
So that's adjusting the aperture
in three different situations.
One on a wide angle lens,
one on a normal lens, and one
on a telephoto lens.
And by opening up the aperture,
making the opening larger,
we shrink the depth the field
in all three of those cases.
It's interesting to see how it's
different for wide, normal, and tele.
And we'll come back to
that in just a second.
So one of the other factors
that effects depth of field
is the distance to the subject.
And what I mean by that is
where your lens is focused.
Generally I'm just going to assume
that we're focused on our subject,
but perhaps not.
But the distance that your lens is
focused at, whether it's near or far
changes how deep or shallow
the depth of field is.
The closer that critical plane
of focus to the film plane
the shallower that depth of field is.
So the closer our subject is to us
the shallower the depth of field
will be versus when it's further away.
It's the inverse.
And a rule of thumb for this is
doubling the distance quadruples
the depth of field so
there's some power law here.
Yeah.
AUDIENCE: [INAUDIBLE].
IAN: Right?
Or halving the distance
cuts it by four, so--
DAN: It's dramatic though.
IAN: It is.
It is.
DAN: And I was shooting some
macro photography this weekend,
and I was at an aperture that was
5.6 six and f/8 and it was so thin.
You think of that depth
field as being fairly deep,
but it really matters how close you are.
With the macro lens you're
right up against your subject,
and so this really is exaggerated there.
IAN: Right, and I think
maybe even that image
that we looked at that was the
green plant with that really
narrow depth of field might
have been on a macro lens.
Let me just go--
what did I do?
I went backwards again.
So this is a wide angle lens
where we're focused at four feet.
Look at the background.
There's a lot out of focus.
We have our little rubber ducky there.
And as we play this video--
perhaps.
No.
And we moved the camera
further away from our subject
racking with our subject, so
keeping the focus on our subject.
Increasing that distance you can
see that the focus in the background
begins to change.
That by increasing the distance
the objects behind our subject
come into crisper focus.
DAN: It's so slow.
It's wonderful.
It's like--
AUDIENCE: Can you play it again for me?
IAN: Sure.
So if you think back to
that duck originally it
was much softer than it is now.
AUDIENCE: So you're
changing focal length.
Are you doing it literally
moving the camera,
but keeping the focus on the subject?
IAN: Yeah.
So what that is doing is essentially
changing where the lens is focused,
and just moving it like this.
As the camera moves backwards
it changes that distance.
So when you look at the starting
position and the end position
you really can see
how soft it originally
was when we were very
close to the subject
compared to when we moved further back.
So this is all, again,
a wide angle lens.
So now we have a normal lens.
We start a little bit more out
of focus in the background.
The depth of field is
a little bit shallower.
AUDIENCE: [INAUDIBLE]
IAN: So if we do our
little comparison again
we can see that distance to subject is
really driving how much depth the field
we have between these two images.
And to do our due diligence
here is a telephoto lens.
Notice how out of focus
our friend the duck is.
And as we move through the scale we'll
see if we can get him to be in focus.
So not quite.
Not quite in focus.
The depth of field is still shallow
enough to keep the duck out of focus.
And this is again a telephoto lens.
And if we do the
comparison between the two
we can see that it's
incredibly out of focus.
Almost unrecognizable to
getting into some sort of shape
that we can understand a little bit.
What is happening?
AUDIENCE: [INAUDIBLE]
DAN: Don't steal my thunder.
IAN: OK.
We'll leave it for a second.
So this is what's called a dolly zoom.
This is where the camera is
moving back as the camera zooms in
at the same time.
So we maintain the exact same
frame over a camera movement.
And what you notice is we actually go
from a wide angle lens with this frame
to a telephoto lens
with this frame and you
can see the actual spatial
distortions that happen in real time
as you change--
OK, one more time.
OK.
DAN: We'll look at this next week
when we talk about video as well.
Yeah.
IAN: So this is--
I really wanted to show
it because it's awesome.
And one of the things that--
our final element of effecting depth
of field or controlling depth of field
is this idea that focal length matters.
That a longer full focal length
yields a shallower depth of field.
So a 150, a 250 millimeter lens on a
full frame camera, a telephoto lens,
has a shallower depth of field
than a wide angle lens, which
yields a deeper depth of field.
And I think we saw that when we looked
at how different each of the elements
were when they were in
wide, normal, and tele.
The wide angle lenses had more
in focus in the background
than the telephoto ones.
AUDIENCE: Regardless of the aperture?
IAN: Yeah, regardless of the aperture.
Well, yes.
So when we were changing aperture--
If we go-- let's-- whoops.
Let's go back here.
So we were changing aperture here.
And you can see the effect
that it has on depth of field.
We didn't change focal length and
we didn't change focus distance.
When we go to here and we change--
let's do this one.
We don't change aperture.
We don't change focal length.
This is a wider angle of view.
This is the camera backing up.
This is just the
distance to the subject.
And you can see the difference
between the elements.
But that is to say that this
image compared to this image
are two different-- this is
us changing focal length,
while all the other
elements stay the same.
We still shifted over distance,
but this is its own unit.
So your rule of thumb for this
is halving the focal length
quadruples the depth the field.
Doubling the focal length
cuts it by a quarter.
That might be helpful
for you in the field
if you want to-- like I need
much more depth of field.
A little rule of thumb
to help you get there.
The interesting thing though
is that in this comparison
when we start at the beginning and the
end is the depth of field different?
And I think maybe we'll
do this side by side here.
So this is the dolly zoom that we did.
We started with a wide angle
lens very close to the subject.
And we didn't change the aperture.
We did change the focal
distance, but then we
moved the camera to a telephoto
lens further from the subject.
So we increased the focal
length, but at the same time
we also increased the
distance to the subject.
And if you look at this
it's sort of apparent,
but it's difficult because
we maybe don't see this,
but the parts that are
out of focus are sort of
similarly out of focus in
both of these positions.
So what that means is that as the
focal length pushed the depth of field
smaller and smaller the distance to
the subject pushed it larger and larger
and they sort of offset each other.
Remember that our rule of thumb was if
you change it by half it doubles it.
If you change it by half--
or if you change it by
half it quadruples it.
If you change it by
half it quadruples it.
And so those two values
actually offset each other.
So for the same frame
focal length doesn't
do a lot to adjust your
depth of field because you
have to change the focus distance.
Does that make sense?
And they actually offset each other.
So if you-- let's draw it.
Maybe that's the easiest way.
So if we have a frame here
and we have a frame here.
And they're the same frame, but for
this one the camera is very close,
and for this one the camera is very far.
And for this one we're at a wide,
and for this one we're at a tele.
We've zoomed the lens out--
this is exactly what a dolly zoom is.
It starts close.
It moves this way and as it
moves we zoom the camera in.
So what we've done is
this focal length is
getting larger, which we know
produces a shallower depth of field.
We're going from a wide to a tele.
And this focus distance, the
distance from here to here,
is getting larger, which we know
increases the depth of field
so it makes it deeper.
And in doing so they essentially
cancel each other out roughly.
AUDIENCE: And that's what gives
that whole effect [INAUDIBLE]
IAN: Yeah, so really
what we're only seeing
is the spatial relationships of
the foreground and background doing
that sort of expansion,
compression trick,
rather than large portions of the
image coming in and out of focus
as the depth of field shifts
throughout that entire element.
So that's just a little aside.
That's like a hiccup where if you--
focal length really matters for depth
of field if you don't with the camera.
Because obviously, you
start to move the camera,
it begins to do less because you change
your focal distance along with it.
Are there questions on depth of field
before we move on a little further?
So one of the other tools in your
arsenal besides a light meter
is this histogram, which
is basically a plotting.
It shows the distribution of
brightness values of any given image.
It can also display the
distribution of color values.
But for our purposes
right now we're going
to look at it as a luminosity scale.
And all this says is that they're--
it reads left to right.
So this is black, and this is
white, and everywhere in between
is some midtone of brightness.
And it just shows you how much of your
image is falling in certain areas.
And so is if this is
full black that means
this area is probably our shadows.
If this is full white this area
is probably our highlights,
and somewhere in here is our midtones.
So in looking at this
histogram we can see
that there's a lot of data
in the dark side of this
with a big spike of
white light at the top.
And there's sort of nothing at the
high delicate highlights or mid tones.
So this is a histogram What do
you think this is a histogram of?
AUDIENCE: [INAUDIBLE]
IAN: Yeah.
So this is a histogram of this.
Just plain white.
Everything is just
jammed up on that end.
So this should warn you when you
start to see your images sort of jam
up towards one end--
towards the right hand
side you're going to end up
with something that's very bright.
What about this one?
AUDIENCE: [INAUDIBLE]
IAN: Yeah, it's this.
It's just this.
Just black.
Inky blackness.
How about that one?
AUDIENCE: Is it 18%?
IAN: Yeah, this is middle gray.
It's this image right here.
Here's one for you.
What's this?
It's a lot of everything.
AUDIENCE: It's going to be, probably,
[INAUDIBLE] highlight [INAUDIBLE]..
IAN: Yeah.
Maybe.
AUDIENCE: [INAUDIBLE]
IAN: Yeah.
It's actually just this gradient.
It's equal parts of
every sort of element
and it renders a very flat histogram.
So what's interesting about
that is this flat histogram
tells you that there's a
completely even distribution
of tones, which sort of suggests
that that's exactly what this is.
It's about as even a
distribution of tones
as you can get in any kind of image.
DAN: Well, [INAUDIBLE],, just to hammer
around the point of how to read this,
this gradient is on the left
black, on the right white,
which is how a histogram
represents its luminosity as well.
But if you were to reverse
this image the histogram
does not read left to
right like an image does.
It would be the same histogram.
IAN: Yes.
Yeah.
Actually that-- yeah, exactly.
'Cause it's just basically
saying that there
is a certain number of
dark pixels in this image
and a certain number of
light pixels in this image.
It doesn't care where they are.
Just there's this much value.
So let's go back to the
histogram that we saw before.
What do you think this
is a histogram for?
Keeps coming back around.
It's like a boomerang.
AUDIENCE: [INAUDIBLE]
DAN: Alec says an outside shot.
IAN: An outside shot.
That's sort of interesting.
Why might we say that?
DAN: Alec also feel free to
unmute and just shout it out.
IAN: Yeah, we can hear you.
AUDIENCE: My guess looking at that would
be like your outside shot that you had
'cause there was so much
shadow detail from--
like in the trees and everything.
IAN: Yeah, totally.
It's the same shot.
It just keeps coming back.
AUDIENCE: You've gotta make points.
IAN: Yeah, that's nice.
So there's not a lot of
highlight value in this image.
There's a little bit of
that snow, but most of it
is this dark tree value, which is
pushing the majority of our tones
into this shadow area, but we see a
pretty decent distribution of tones,
and we have some highlight values,
and we have some shadow values.
DAN: And the very rightmost
pixel here, on the right side,
we also have this indicator up here.
And it looks different
in different software,
but this is the clipping
indicator meaning
that something is fully overexposed,
meaning that it's true white.
IAN: Yeah, and it honestly is the--
it's the middle section in here.
Like there's some small amount of
that that's clipped out pretty hard.
AUDIENCE: So when you say clipping that
means like there's like [INAUDIBLE]??
IAN: Yeah.
So as you try to render
tones in an image
you can essentially push up
against the maximum value, which
is like it's so bright that it hits the
maximum recordable value for the camera
and then there's just no more data
to record so it just is at max.
AUDIENCE: [INAUDIBLE]
IAN: It's at full, which is usually--
like clipping over exposure.
It will show up as white
because it's maximum red,
maximum blue, maximum green.
It's just pinned at the top.
AUDIENCE: [INAUDIBLE]
IAN: Yeah, exactly.
And the opposite is where it is
just crushed down to that black.
And that's what those two extreme
examples of the white histogram
and the black scram were.
Where there was-- like
all the values were just
pinned at either the left or the right.
Either the maximum highlight value
or the minimum darkness value.
And so once you clip though you
can't get that information back.
It's lost.
There's no way to bring that back.
If you try to do any correction
on that and bring the tone down
it's just going to shift in
grayness 'cause there's no detail.
It's just bright white.
It's a flat white field,
and if you bring it down
it just will be a flat gray field or
you go all the way down to a flat black.
So if we look at this
here histogram, which
is the idea of a low key histogram
it's pushed to which side?
AUDIENCE: The left.
IAN: Which is?
AUDIENCE: Shadows.
IAN: Shadows.
And we've got some midtones.
Not really a lot.
AUDIENCE: Very little.
IAN: Yeah.
And we have some highlights--
AUDIENCE: And there is a
peak of light seek of white.
IAN: What's that?
AUDIENCE: There is a peak of
white somewhere in there as well.
IAN: Yeah, there is a
little bit of brightness.
You can see it ticks up just at the end.
Just a little bit there.
So what do we imagine
this image looks like?
DAN: [INAUDIBLE] says, underexposed.
AUDIENCE: A white dot on a dark wall?
IAN: A white tall and a dark wall?
Yeah, something like that.
Yeah.
So there's some small amount of
brightness in a large dark field.
That was a pretty good read.
This is probably our white values.
There's the tiny bit of mid tones that
we were getting and the rest of it
is falling off into these very
distinctive shadow details.
So you might have looked at-- if you
look at this histogram, like all tools,
it can be fooled.
This was an intentionally exposed
image to have all of the values--
to have this be dark.
To have everything pushed
to the left because that's
the sort of the composition that
this photographer was going for,
but if you were sort of
just looking a histogram
you'd be like no that's not right.
I'm looking for an even
distribution of midtones.
And I think you'll find a lot of people
suggest that that's the correct way,
but it's not always.
It does matter about your intention.
So the flip side of this
is a high key histogram.
It's pushed to which side?
AUDIENCE: The highlights.
IAN: The highlights.
DAN: And just to say
plainly we're looking
at an overlay of
several histograms here.
Different color channels.
And then the gray one
represents the luminosity.
IAN: Right.
DAN: But that just depends on
which software you're using
and what options you have turned on.
IAN: Yeah, and so you can get
a variety of different scopes.
And actually that's a good point.
So the earlier version
that we were looking at it
was the histogram from Photoshop
and this is luminosity and color
like a compound
histogram from Lightroom.
And so you have different options
that you can turn on and turn off.
And sometimes for certain
images having the color
on shows you a cast or a skew that might
be in there especially if you did not
set your color temperature.
So what does this image look like?
AUDIENCE: Bright.
IAN: Bright.
Right.
I think we can safely assume that.
There's not a lot in here that
is actually a deep dark color--
dark tone.
It's mostly whites.
Bright sky highlights.
There's some grays in there.
There's not even really a solid black.
Maybe a little bit of a
shadow detail in there.
And so when we look at the
histogram you really can see this.
And so again we're not
using an even distribution
but we understand that this
is correct for our subject.
Sweet.
So putting it all together.
Here is an image that is overexposed.
This image is mostly white.
The values up here are
completely clipping.
It's solid white, but it's OK
because it's the point of the image.
So this is an intentionally
overexposed image.
We could meter this and
the camera might try
to tell us to make this a middle gray
because it thinks that's what we want,
but we know we're smarter than it.
So we're going to increase the exposure
so that pushes up to white and in fact
clips.
And we get an interesting
shot of these sunglasses.
Solid marketing.
So then the flip side is this
is intentional under exposure
where we've decided to
not expose for this value,
but actually for this white value
and give ourselves a silhouette.
DAN: Do you have a
histogram for this one?
Like what does this histogram look like?
IAN: I don't.
I could get it in a second, but I don't.
I don't have it.
DAN: It's split though
right? 'Cause we have--
IAN: Yeah, it is split.
DAN: --very little in the middle 'cause
it's almost all largely the bottom
because the histogram represents
like 100% of the pixels in the image.
Most of them are in the
dark so that's going
to be where our biggest mountain
and the highest peaks are.
And then we'll have also a
big spike up on the right
because the white screen in that
image was almost fully overexposed.
So histograms I think--
most cameras have histograms
on them when you're shooting.
If you pull up your digital screen and
push the button to pull up the display
you can cycle through different
overlays on your screen.
And so histogram is an option,
but I find that they're
much more useful in post-production.
When you're actually
shooting I think the thing
you typically want to look
at is your light meter
and to know if you're getting
a good exposure or not.
And obviously you'll
either intentionally
add exposure over or under, but
at the end of the day histogram
is helpful when you want
to look at overall trends
once you get to post-production.
And really to check if you are clipping
any information at the highlights
or in the shadows.
I think that's really where
the histogram is best served.
IAN: Yeah, and I think
actually, I also tend
to check the histogram
early when I'm shooting,
but when I'm pushing exposure in
an image like this or an image
where it's really bright and I'm going
to maybe push up against overexposure
or clipping I will look at
the histogram at that moment.
When I know that I'm compensating
and I want to make an image brighter,
and I want to push it up
towards that bright white value
I want to make sure that
I don't clip because I
can't get that information back
so I want to get as close to it
while still maintaining
some detail in the image.
So it's a really good
tool for when you begin
to experiment with pushing
and pulling your exposure
away from what the light
meter is telling you.
At the end of the day 90% of the scenes
that you photograph the light meter
is going to do an amazing job at
calculating some calibration for you.
AUDIENCE: It'll get you really close.
IAN: Yeah, it'll get you really close,
but you then have to make a decision.
Do I accept this, or do I
push one way or the other?
DAN: And the other thing I'll just say,
since we're talking about histograms,
is the useful thing-- the
indicator that popped up.
In post, and we haven't covered
Lightroom in this class,
but if you're using something
like Lightroom or Photoshop
typically if you hover over the
indicator that you're overexposed
it'll show you an overlay on the screen
where which portion of your image
is clipping.
And it's just helpful to get a read
on exactly which part of the image
is over or underexposed.
So I think that's the tail end of
our conversation about exposure.
I want to stop for a
minute and see if there are
questions from anyone in the audience.
What questions do you have?
AUDIENCE: I have a question.
IAN: Yeah, go for it.
AUDIENCE: When you introduced histograms
programs Dan just briefly mentioned
this, that we can see a
histogram in our viewfinder
or on the screen in our cameras?
IAN: You can in a large
number of cameras.
I think this is now turned off.
So let me just fire up this camera.
We can take a look.
So this is the output of
the 5D and it's currently
shooting this bright white wall.
And you can see that
the histogram is pinned,
except when I walk in front of
it, right to the right hand side.
But if we do something like
maybe introduce another tone--
again, this is over exposed-- we can
see that the histogram starts to move--
this is a darker tone--
in real time for what
it is that it's seeing.
So in this image I would
look at this exposure
and I would know that if what
I want is a bright white field
I have successfully exposed this image.
But if I don't want that--
if I want some kind of detail
I'm going to adjust some values.
Like maybe I'll close
the aperture down, which
you can see I'm doing on the bottom.
And I'll change the exposure so that
now I don't have a bright white field,
but I have a middle gray field.
And I know that it's
rendering as middle gray
because right in the middle of the
histogram there's this giant peak.
I think-- can you push the talk?
AUDIENCE: Sorry.
IAN: That's all right.
AUDIENCE: So I assume you have to be
on a manual mode in order for this--
to see a histogram and alter
all of these different--
IAN: It's actually just
one of the info features.
I can actually turn off
all of that clutter.
If I press it again I get
it without the histogram.
I get some extra data.
And then I can turn the histogram on.
So your camera may or may
not have this feature.
Most do at this point.
So there should be either a way to
turn it on in the menu or a button
that functions to allow you
to turn this on so you can get
a sense of what you're exposing for.
DAN: And Lorna, your camera may
not have it in automatic mode.
You might need to be in
a different camera mode.
And we did record a short
video on camera modes
so check that out after this
lecture if you have more questions.
And if I can just speak experientially
for a second with histograms.
Like I said I think when
you're going out to shoot--
I don't find them all that
useful when I'm shooting,
but the times that they are useful--
if you're shooting a bright sun
and can't quite get
a read on your screen
and you want to know if you're
overexposed on your highlights it's
really helpful in that moment, but for
the most part when I go out and shoot I
am using exclusively the camera meter.
IAN: Yeah.
And I think that's a good point.
Just like it's sometimes very hard
to assess your focus on a very
tiny monitor or through a viewfinder.
It can be difficult. It can also
be very difficult to see a LCD
screen in bright sunlight, which is
I think what you're talking about.
And that the histogram sort of proves
to you what is happening in the image
because it's not based
on some visual cue.
It's based on the actual
data in the field.
So again there's a video
on light metering more
generally and how to trick
and fool your light meter,
and also one on camera modes, which
I would encourage you to watch
for the next assignment because
there's a couple-- we're
going to ask you to experiment with
the different elements of exposure.
And you can use either aperture
priority mode or shutter priority mode
to help you play with that
as well as full manual
if you're feeling brave
and adventurous, which
I encourage you to feel at this point.
Any final questions or parting thoughts?
Well, we'll stick
around for a few minutes
and let us know, but thank you all
very much and we'll see you next week.
