What is the best aperture for video?
It’s f/2.8, or T2.8 if you are thinking
T-stops.
You can stop now and watch another one of
my amazing one second videos.
Or
You could stick around and I’ll tell you
why f/ or T2.8 is the best aperture.
Are you democratic?
Then you’ll be easier to convince.
I’ve studied the work of hundreds of cinematographers,
and the T-stop they light to most of the time
is T2.8.
This corresponds to about f/2.5 or thereabouts,
but you can assume it’s f/2.8, for the sake
of your sanity.
Why do cinematographers pick T2.8?
Four reasons.
The aperture number, called f-number, decides
how big the aperture opening is.
The higher the number, the smaller the aperture,
and the lesser the light hitting the sensor.
Cinematographers always had to fight the low
sensitivities of film stock.
They were working with an Exposure Index of
50 or 100 most times, even today.
The corresponding ISO is about double the
exposure index, according to Kodak.
So they didn’t have the ISOs modern cameras
have.
This meant they had to open up the aperture
for good exposure or use too much light.
Too much light would have cooked film sets
and the actors, well over legal tanning limits.
They had to strike a good balance between
practical lighting and what is tolerable.
T2.8 was a good happy medium, just short of
war.
And this is just one reason.
The second is when you open up the aperture,
you get shallower depth of field.
If you stop down or close down the aperture,
you get deeper depth of field.
This is why movies like Citizen Kane had to
use tons of light, for their deep focus look.
If you want everything in the frame to be
in focus, you must stop down the aperture.
This cuts light by a tremendous amount.
Every step in the aperture scale cuts one
stop of light, or double the light.
The other end of the spectrum is shallow depth
of field, where you have no clue where the
actor is.
To get this effect you open up the aperture
to its highest rating, sometimes T2 or T1.3
on traditional cinema glass - if you had the
option.
These lenses were available back in the day
when cinematographers used T2.8.
The Godfather was shot with Bausch and Laumb
Super Baltars that were T2.3, and Taxi Driver
was shot on Zeiss Super Speeds that were a
T1.4.
Some scenes in Taxi Driver were shot wide
open, especially the night shots, you can
see the distinctive triangular bokeh, which
was not always popular.
So why didn’t these cinematographers open
the aperture all the way if they could have?
There’s no free lunch.
Lenses in those days weren’t as advanced
as today, so if you opened the aperture all
the way, you had three major problems.
First, you had too much flare.
Flare is not just those cool streaks of light
you see, it’s also a loss of contrast.
Imagine going through all the trouble of learning
about film stock and lighting, only for something
stupid like lens flare to ruin your shot through
lack of contrast.
The second problem was also serious.
The lenses weren’t that sharp wide open.
This is true of almost every lens on the planet,
with a few rare exceptions.
Lenses are not the sharpest when wide open.
The general rule of thumb is the lenses have
to be stopped down by two stops for best sharpness.
E.g., if you had an f/1.4 lens, you had to
stop down to f/2.8 for best sharpness.
This also meant if you used different focal
lengths, the sharpness across the entire range
matched.
This is the biggest problem with cheap lenses
that open to f/1.4 or higher today.
They don’t match across the entire set.
Great cine lenses like the Arri Master Prime
series open to T1.3 across the entire range.
You’ll never find an equivalent photo lens
series that all open to the T1.3, at any price.
The Master Primes are known to perform very
well at T1.3, they are sharp and cinematic.
But even these lenses are sharper stopped
down to T2.8.
The last reason cinematographers stopped down
was probably the most important one.
Shallow depth of field also meant focus pullers
had a terrible time following actors.
Remember, they didn’t have monitors in those
days.
Focus pullers had to use all their experience
and concentration to keep a moving actor in
focus.
Today, there are aids, but unfortunately higher
resolution has balanced that out.
Focus mistakes are way more obvious in 4K,
and even so in 8K.
So whatever advantage monitors and electronic
systems have introduced, higher resolution
has taken away.
It’s still hard to focus moving subjects
at T1.4 in 8K.
Force focus pullers to do that, and there’ll
be a contract out for your life.
T2.8 provided cinematographers the best balance
between shallow depth of field and deep focus.
You could make out the background, so you
were still in the story.
This trend is still followed today by most
cinematographers.
Nobody wants a completely shallow depth of
field, otherwise it will look like it was
shot in a studio.
The third reason to pick T2.8 is, very few
people can afford deep focus.
When I shot Man May Love, I stopped down the
Arri Master Anamorphics to T8, and compensated
by raising my ISO to 6400, which is the limit
for the Red Monstro.
Even then I felt I didn’t have enough light.
There is another problem with stopping down
the lens.
When you cross a certain threshold, typically
f/11 for Super 35mm sensors, you lose sharpness
again.
This is called diffraction, and the explanation
is quite technical.
All you have to know is, just because you
can stop down to T22 doesn’t mean you should.
You’ll get softer images.
Just like with everything else in life, a
happy medium is the best for the aperture
as well.
And it’s not like cinematographers sat down
and decided these things cerebrally.
It came about organically, through practical
limitations of cinematography, cameras, lenses
and lighting.
But what they got in return was the fourth
reason, the ability to stay consistent with
their lighting and exposure.
They could achieve the great effects we love
so much, even in the high-stakes, high pressure
environment of a Hollywood film, because they
were able to keep some things constant.
This is why, over a hundred years of cinema,
T2.8 is the most preferred aperture for normal
lit scenes.
For low light night scenes, cinematographers
typically preferred T2.
Before.
That is no longer that relevant today due
to the improvement in ISO and sensitivity
in digital cameras.
So, T2.8 or f/2.8 is the best aperture for
filmmaking, if you’re feeling democratic.
Look at the classic popular zoom lenses for
cinema, they are close to T2.8, T2.95 or T3.
Even photography zoom lenses are consistent
across all brands at f/2.8.
Look at B&H, even they let you find lenses
with apertures above f/2.8 or higher, because
they know that’s the threshold.
You can open the aperture as wide as you want,
or you can stop down as much as you want.
Not everybody sticks to T2.8 all the time.
There are always exceptions.
If you like T2.8 please hit like, if you prefer
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