What is exposure triangle?
Exposure triangle is an analogy ‘gurus’ use to initiate beginner photographers and cinematographers into the ways of the aperture, shutter and ISO.
Why do people need an analogy? Because it’s confusing. Look at the markings on a lens:
Most curious minds who see this at the beginning are immediately turned off. I’ve seen many eyes glaze into the horizon when I start to explain the aperture, shutter and ISO.
I gave up photography for a couple of years after watching someone else’s exposure triangle analogy (won’t tell you who). Now, many years later, I feel I am obliged to try my own hand at it.
But – without any triangles or analogies. Here it is straight: Exposure Triangle, explained for complete beginners.
And, how to use the Aperture, Shutter and ISO to create cinematic images:
Attributions and References:
- Music by Audionautix.com
- Traite Enclyclopedique de Photographie, by Charles Fabre, 1890
- A History of the Photographic Lens, by Rudolf Kingslake, 1989
- Kodak’s Chronology of Motion Picture Films
- IMDb
What is the exposure triangle?
The exposure triangle is just a way of saying the aperture, shutter and ISO are all related to each other.
But – the triangle has nothing to do with it.
Even as a symbolic thing, it’s more confusing than enlightening.
What is aperture?
Aperture or Iris is the ‘gate’ that blocks light from hitting the sensor. The beauty of this gate is that you can vary the size, thereby letting more or less light in.
When you want more light in, you ‘open up’ the aperture. When you want less light in, you ‘close down’ or ‘stop down’ the aperture.
Aperture numbers are written as:
f/0.7, f/1, f/1.4, f/2.8, f/4, etc.
The ‘f/’ is to show these numbers refer to the f-number and are not to be confused with the numbers on the focus scale.
The ‘/’ is to show the numbers are inversely related to the size of the aperture. The larger the aperture, the smaller the aperture. E.g., f/1.4 is a larger aperture (more open) than f/16 (more closed).
Why are f-numbers called f-stops?
F-numbers can be any number: 1, 2, 3, 456, 7 million, anything. F-stops are numbers where each subsequent number is a stop higher than the previous one. You can also have half stop increments and a third-stop increments.
A stop is double or half the light. E.g., if 100 lux is light falling on a table. A stop higher is 200 lux, and a stop lower is 50 lux. The f-stops, the ISO and shutter speeds are all controlled in stops, half stops or a third-stop at most. Greater accuracy than that isn’t required.
A serious student of photography and cinematography is encouraged to think in terms of stops. Cinematographers who light film sets also talk to their gaffers in terms of stops. It’s a good habit to have!
Now that you’ve understood what an aperture is, go into slightly more detail here:
What is shutter?
A shutter is a ‘second aperture’, but with a timer on. You decide how much time the shutter stays open.
Shutter duration is measured in seconds, minutes and hours – whatever’s convenient.
Why do people call it shutter speed and not shutter duration?
I don’t know the exact answer. Some things are lost forever. However, the word ‘speed’ (as in film speed) is related to the sensitivity of light. Maybe this is why people call it shutter speed. You can call it shutter duration or just shutter.
What is the relationship between the aperture and shutter?
Both aperture and shutter let light in (or block it out) – in a controlled manner. The difference is:
- Aperture – shape bound (space)
- Shutter – time bound (time)
The reason both are used is simple: Aside from controlling the amount of light, they give different effects:
- The aperture controls depth of field and other image characteristics.
- The shutter controls motion blur, thereby sharpness.
Both are creative tools as they are functional ones. There’s nothing stopping tomorrow’s technology from combining both into one system.
Just remember this:
The primary creative job of a photographer and cinematographer is the manipulation of aperture and shutter to get the effect he or she desires. This is the very core of camerawork.
To get a more in-depth look at shutter speeds, start here:
What is ISO and why do we need it?
ISO is a measure of sensitivity. The greater the number, the more the sensor or film is sensitive to light.
What does it mean to be sensitive?
In lay persons terms, it means the sensor can see better in low light. The darker it gets, the better it can see.
Here’s a camera that can shoot in the dark, in faint moonlight and nothing else:
Why do you need an ISO?
Both the aperture and shutter have limitations. Together, they can do many things, but there are many situations where the combined power isn’t enough.
It’s at that point you can ‘nudge’ the ISO a bit – move the goal post so to speak.
Today’s modern cameras can create stunning imagery over a range of stops with ISO, and in the future it will only get better.
To learn more about ISO, start here:
Summary
The exposure ‘triangle’ is just a system beginners use to learn the relationship between the aperture, shutter and ISO.
I hope my simple explanation has helped your understanding. If you feel some other beginner might benefit from this knowledge, please feel free to pass along the video.
