Hi I’m Sareesh Sudhakaran.
In this video I’ll show you why lighting
contrast ratio is so important to cinematography,
and how high key and low key styles are defined
specifically in filmmaking.
Lighting contrast ratio is the difference
in stops between one part of the image and
another.
A face can have a lit side and a shadow side.
The difference between the lit side and the
shadow side in stops of light is the contrast
ratio.
E.g., you place the light meter on the lit
side and it reads f/5.6.
Then you place the light meter on the shadow
side and it reads f/2.8.
This means the lit side is two stops higher
than the shadow side.
I say the contrast ratio is two stops.
So, in many ways, you are comparing two things,
but the word ratio doesn’t hold a lot of
importance here.
It’s more of a difference between the two
sides rather than a ratio.
Photographers have a ratio system to measure
contrast ratios.
2:1, 3:1, etc.
That system is not used in cinematography
and gaffers don’t talk that language, so
learning to communicate about lighting in
stops is important.
If the key and the shadow are the same exposure,
then we call it flat lighting.
If it’s only half a stop above, the contrast
ratio is half a stop.
For really moody and dark scenes the contrast
ratio can be 4 stops or higher.
Gordon Willis frequently used large contrast
ratios in his lighting style.
The typical average is about two stops, though
it varies from scene to scene, depending on
what the cinematographer is trying to achieve.
The lighting contrast ratio on the face is
only one half the story.
The other contrast ratio is the difference
between the lit side or key, and the background.
It is also measured in stops.
The most common technique used from the earliest
days of cinema is to have the background one
stop darker than the subject.
Now to understand high key and low key lighting,
let’s take some common scenarios.
You could either have an overexposed foreground
or background, an underexposed foreground
or background, and a middle exposure, let’s
just call it grey for now.
I’ll use the words black and white for the
other two, but please remember it doesn’t
have to clip to white or black.
I’m just doing it for simplicity.
Grey actually means the range of about two
stops over and under middle grey, so there’s
a grey area.
Get it?
Grey area?
Don’t pardon the pun.
Why should puns be pardoned?
With these three possibilities, you get a
total of nine combinations.
You have black-black, black-grey, black-white,
white-black, white-grey, white-white, grey-black,
grey-grey and grey-white.
Say that back five times.
Let’s say you have grey-black.
This is called low key lighting in cinematography.
By the way low key and high key are understood
differently in photography and cinematography
for some reason.
I use it the way I’ve learned it from books
and cinematographers interviewed in ASC magazines.
Going forward, what if the subject is overexposed?
Against a dark background, it’s always low
key lighting.
Black on black is also low key.
It’s very easy to remember low key lighting.
When the background is dark to the point of
underexposure, or actually underexposed, or
even black, it’s called low key lighting.
Such lighting is used to create a sombre or
sad mood.
I have a whole different video about low key
lighting you should check out.
I’ll link to it below.
Now let’s go in the opposite direction.
When the subject is correctly exposed or overexposed
against a bright background, we have high-key
lighting.
High-key lighting is used in many sitcoms
and comedies, because the world is always
a cheerful place.
It’s easy to remember because the background
will be brightly lit and cheerful.
No unnecessary shadows to spoil the mood.
Cartoons are a great example of high key work.
If you have a white background or grey background,
by which I mean about two stops above or below
middle grey, but the foreground is underexposed
or even black - it’s called a silhouette.
There’s no ambiguity.
All this is common knowledge on film sets.
If we have a grey background with either a
grey or white foreground, it’s just normal
lighting.
This is what the majority of scenes look like.
Remember what I said about contrast ratio?
If everything is in the realm of grey, the
background is one stop below on average, which
is below the two stops we need for grey.
Up to two stops is fine.
More than that and the look gets moody and
serious.
You don’t particularly refer to high key
or low key in reference to contrast ratios
on a face, though naturally they fall into
the same rules when you light the set.
The fill side or shadow side will generally
match the background.
It’s rare to have a dark shadow side but
nowhere in the room is it that dark.
That will look unnatural.
So there’s no need to look at the face for
high key or low key lighting.
You look at the background.
That tells you everything you need to know.
This is specific to cinematography because
in cinematography you are lighting spaces
and scenes most of the time.
All the shots taken in that scene and space
have to match.
Getting the mood right is critical.
To wrap it up.
Contrast ratio is the difference in stops
between the key and the shadow.
High key is when the background either matches
the foreground in correct exposure, or if
the background is overexposed.
Low key is when the background is underexposed
or black, regardless of what the subject looks
like.
And finally, the silhouette is a special case
where the background is correctly exposed
or overexposed, but the foreground is underexposed
or black.
Everything else is normal lighting, by which
I mean the kind that doesn’t contribute
a lot to manipulating the mood.
That’s it.
There are no other variations possible.
Sometimes you fall into a grey area, but that
doesn’t really matter because the cinematographer’s
eye and experience will tell them what the
mood is like.
After all, lighting is just one aspect of
mood.
Humans also use other cues like the actor’s
wardrobe and expression, and the context of
the scene, what’s happened before, etc.
The best example I can think of is The Shining,
in the bathroom scene.
It’s lit to high key, but the mood is anything
but.
And for the reverse study Manhattan, where
the lighting is mostly low key, but the subject
is comedy.
You can break the rules as much as you want.
