okay guys pop onto blackboard download
the files that are there. You are gonna
be working on an assignment which you
will get today and I will show you
examples of what people have done in the
past where you're gonna be taking a can
and you're gonna cut it out today, but
then you're gonna photograph some kind
of background and you're gonna
composite it into that background
including whatever shadows or
reflections or whatever are necessary, so
we're gonna go through the whole process
of getting that created. So to that end
take a look on the screen there.
Something has been added to that scene.
What do you think it is? I said can
didn't I?  I know you would have figured it
out anyway. But you'll notice it's a
pretty good job and this is kind of the
gist of what the assignment is gonna be.
You're gonna be photographing something,
so the student in this case photographed
the refrigerator. They already had the
can cut out because that's what we're
gonna do today... our plan today is to get
this can extracted using a channel
masking technique and we'll put it on to
some kind of a synthetic background that
we'll make up, we'll put in a little
reflection... all kinds of stuff. This one
didn't have a reflection but it did
include a shadow... like for as far as
realism goes you want to include as much
stuff as you can to make it look as
realistic as you can, so I'll show some
examples of what people have done
in the past, but you see there's the can
just kind of magically levitating in the
fridge. So there you go.  How are we gonna
do that?
Well pop onto blackboard download the
files and in there you'll see two little
SanPelli files. One is the can itself and one is a
different version of the can. Open them
both up in Photoshop and let's talk
about these two different images here
these were made by Paul Eekhoff for one
of the studio classes and the idea was
to try to figure out how you
could cut out something with fairly
complex edges without having to resort
to doing a whole lot of complex cutting
out. Remember we took a look a while ago
at using a layer mask? You grab a
paintbrush and you kind of cut out around
the outside, then you select the
background, expand and fill... all that kind
of stuff. This will be a different
technique this will be using something
that already exists and trying to make
that into a layer mask. We've talked
about the RGB concept (red green and blue) and how you have three
different color channels. Have you guys ever heard the term alpha Channel?Basically,
any channel that doesn't contain
color information, and we use it in
Photoshop to store selection information. Other programs use it for other things
like if you're doing 3D rendering, an
alpha channel would be used to represent
transparency, but for us it stores
selection information. Now what are we
going to do about getting this can cut
out I mean like I said we could use a
pen tool or we could go in with a layer mask and we could take that
paint brush and we could try to match
the softness of the edge
I'm guessing this softness is... well
that's too soft of an edge...
What happens if you try to cut out using too soft of an edge? Let's say I'm cutting
out along here and I get close to the
can... if I don't go far enough I'm gonna
leave a little bit of the background
showing if I go too far... I want to get
rid of all that background... Oh! I've made
some of the bottom of the can there
invisible... we want a nice clean edge
around there. If I was using the layer
mask, I'd probably take a brush about
this size. That would be a good,
appropriately sized brush. But imagine
this was a model standing, you know
against the sky and the hair is blowing,,,
would this technique work to cut out hair
really convincingly? Probably not. A
channel mask though... if the background is
fairly smooth can do it. Now this image... a
channel mask isn't really going to work
because there's no channel that has
really good contrast between the
foreground and the background and that
is why Mr. Eekhoff included... this
photograph. How did he do this?
Did he just under expose? What do you
think? He shut off the front light. He's got
a background light shining onto here to
light up the background ,he's got a light
in the front lighting up the can. He just
turned off the front light and got this
silhouetted version of it. Now a layer
mask that cuts out that can... what would
that look like? It would be... if it's
revealing the can and
hiding the background (white reveals
black hides) so it'd be a white can with a
black background. We've kind of got a
black can with a white background....
Ooh! That's almost the exact opposite of
what we need! we can really easily invert
stuff,
can't we? So this is actually a pretty
good starting point for a layer mask.
Would it be a good mask though? Pure
black would hide. Let's zoom in
here and take a look.
You don't see it so much here, but let's
look at the individual color channels.
Here's the red channel. Here's the green
channel and here's the blue channel. I
don't see it so much on the projector,
but you can just barely... look at this, see
this detail in here? That would be bad.
That would be partially transparent on a
layer mask. And if you go over to the
other side of the can... oh, there's some
even worse bits around here. And the
background, which would need to be pure
white... it's pure white over here but, oh...
look at this. You start seeing this
gradient pattern making its way across
and it's actually, you know, kind of
bumping up against the can. So there
actually is some gray tones here and
some gray tones there. A proper layer
mask would be completely black to hide
or completely white to reveal. Could we
make this completely black or completely
white? Yes we could. Levels. What if we
pull the levels in? Now, we've got a red
channel, a green Channel and a blue
channe,l and if you're doing a channel
mask on, say that woman standing on
the hilltop with her hair blowing in the
wind if you did it directly to one of
the color channels you'd be messing up
the colour information in the image,
wouldn't you? But we could only load up
an alpha channel, so we need to make an
alpha channel, but we want to base it on
one of these colour channels. Typically
with people, you'll usually find it's the
blue Channel, and actually on this one
here the blue channel also seems to work
out best. So call up the image, the "SanPelli_Silou"
image, the silhouette image and go
into the channels there and if you click
on the names of the channels (red, green,
blue) you can see each individual channel.
And take a look in the shadows of that
label and see that information that's
showing up in there... especially on the
red Channel... you really see some of these
gray tones showing up in the label there.
The blue channel seems to have about the
best contrast, so let's go to that blue
channel there and we're gonna have to do
some horrible things to it. We're gonna
permanently lose some shadow information
and some highlight information. So what
do we do to that blue channel? We don't
want to do it to the blue channel. Let's
duplicate it. Now, there's a couple ways
you could duplicate it. They'll both get you to the same end result. One
we'll do it a little bit more
expediently. If you right-click and
choose duplicate layer,
it'll duplicate the channel, but you'll end
up with the wrong channel visible.
Take a look on the screen for a second
If I right-click and choose duplicate
channel... it does it. Awesome. There's that
copy of the channel (and it even called
it Blue Copy for me which is awesome) and
you can see that it's highlighted in a
lighter gray meaning this is the active
Channel... but it is not visible. The blue
channel is visible. I could make it
visible simply by clicking on that... the
Alpha Channel is now visible, but because
it's not a color channel it shows it as
this kind of red overlay (it's called a
Rubylith... it kind of dates back to the
days of the dark room) but if I turn off
the eyeball in the blue channel, all I'm
seeing is the blue copy here. Another way
to make a duplicate of the blue channel
is to simply grab it and drag it down
onto the new channel icon right between
the trashcan and the other little icon
there, and Voila! It gives you a blue copy
with its eyeball turned on and it's the
active Channel. So we have an alpha
Channel. Like I said, we have to do
horrible things to it. We have to do a
permanent change and you might say "well
why don't we keep this non-destructive?
Why don't use an adjustment layer
for our levels here?" Why don't we use an
adjustment layer? We're in the Channels Panel...
We can't use any layers in here, so it does have to be done directly to this. So let's call up our levels....
let's go under Image - Adjustments and
Levels (or the keyboard shortcut for
levels? Command-L. either will do. Image -
Adjustments - Levels or Command-L. Now
let's look at this histogram here. Here's
our can... here's our histogram and here's
our shadows. This is our can here and I'm
guessing this little part along here is
our can. We saw that you can see the little
little flecks of grey along the edge
there, that's probably these little guys
around here. If I grab this black point
and pull it up, any of this tonality that
ends up to the left of the black point
will become black so I pull this up...
there we go. Oh no! There's still a little
bit more in there! sneaky stuff... Okay,
around 23... 24... wow, for me seems to deal
with that crud along there. Now the
highlights... you can see this gradient
kind of making its way across and the
white over here...
awesome, cuz like, that spotlight was
really blasting onto the edge there, but
that fall-off... we're getting some
tonality in here which would be this
stuff around in here. Well let's take
that white point and pull it down... not
too far. We don't want to crank it down
this way... just enough that that grey
recedes enough that we have white around
the outside here. It's like a festering
gum line, we want to kind of recede
enough that we can see white around the
entire side of the can. Now this is going
to be a permanent change so think
carefully about what you're about to do
before you hit okay. And that's all we
really need from this silhouette
document. You can call up channels
between documents. If we go back to the
original SanPelli image, and we go under
select load selection and... it found
the silhouette document because it knows
it's the only one with an alpha Channel
and it said "well this must be the one
you want... there's no other options in
here". So I'm gonna hit OK and kaboom, we
have loaded that alpha channel as a
selection. So far so good. How's everybody
doing?
So if this had been a person
standing... you know, that woman on the blue sky and the hair blowing,
you could find the channel that has the
best contrast, play around with the
levels, load it up as a selection, hit it
with a layer mask... Would it be perfect?
Probably not, but it would be a pretty
good starting point, and that's what
we've got here, is a pretty good starting
point. So when we have an active
selection and we create a layer mask the
layer mask will be based on that
selection. So, hit that layer mask icon...
Kaboom... and it's backwards... Remember I
said... yeah, the can would have to be white
to be revealed and the background would
be black, well we've got a black can and a
white background. What's a fast way to
invert that? Command-I or Image -
Adjustments - Invert, and around it goes. So
far so good. We're getting there. Now, that
was pretty quick and it was pretty good
for... look at this. See the edge of
the can here, it's got like little
water droplets and look at the detail of
those little droplets along the edge
there. That was pretty good. This side
over here... uh-oh. Oh no... look at this.
We have transparent areas. We have holes
in the side of the can. The soda
would leak out through those areas. What
caused those little holes? Let's take a
look at the layer mask for a second. Why
do we have little holes along there? Yeah,
When the background... it was really bright.
Like, if I look at the layer itself
for a second... Yeah, the light was blasting
onto here and some of it was reflecting
off of the edge, so some of that white
actually got reflected into the edge
here. That's okay, we can change the layer
mask at any time. There's nothing
permanent about a layer mask, so I could
go in here with a paintbrush... black paint...
a hundred percent opacity and in this
case probably a hard edge, and I can just
kind of paint some of that stuff out. Now
we can see the little edges of the
little bubbly bits along there and you
guys remember the shift-clicking
technique... if I hold down the shift key I
can jump between points. So that lets us
bring back those visible parts of the
edge. So give that a whirl. Okay, so guys
once you've got the side done, take a
look around and see where else there
might be problems... like could there be a
giant PVC pipe sticking out the bottom
of the can? Yes there is.
Can we visibly see where the edge here
is? No we cannot... unless we option click
on the layer mask. You can paint on a
layer mask whether you have it visible
or not, so from here I can see...uh oh,  big
pipe going up the bottom side there... I
can click my way around and cut that off.
Ultimately, what we're trying to get is a
can floating magically in transparency.
So work your way all around the image...
You'll also notice the left side...
remember we pushed the whiteness until
it just went around the edge of the can
there, so we had white around here? Now
that we've inverted, it's black but all
of this stuff is still here. This is
where a big honkin brush could help and
we can just paint down the side there
and then zoom in and do the little
finicky detailing bits. When you're
painting on a layer mask, make sure you
have the layer mask selected... like these
are the four corner points are around it.
if you've got the latest version of
Photoshop, sometimes when you step
backwards... Let's say you do something and "oops let me just undo that", (Command Z) it
drops the focus from the mask onto the
layer itself and then suddenly you go in
with paint and you're painting on the
layer itself, not on the map. Because
Adobe likes to piss people off and
they're getting very good at it. In one
of the later versions you'll be
painting on the layer mask "oops, let me
just undo that" Command-Z, and suddenly
you're painting black across your image
and if you're doing white you may not
necessarily notice that you're doing it
on the image itself or if you're in a
gray area... so yeah, good for them right?
 
