What is the Exposure Triangle?
The exposure triangle is a way of visually depicting the relationship between the three variables that, together, control exposure – ISO, aperture and shutter speed. They are represented together as a triangle to illustrate that if you change one of the variables, you need to change the other if you want to keep the same exposure.
Here’s an Example.
Suppose a proper exposure has an ISO of 100, an f/stop of f/5.6 and a shutter speed of 1/125 of a second.
But you decide you want to increase the depth of field. So, you change the aperture by one stop from f/5.6 to f/8. This darkens the light coming through the lens and, if you don’t do anything, darkens the exposure by one stop. To keep the same exposure, you have two choices. You can change the ISO or the shutter speed.
If you changed the ISO you would have to change it from 100 to 200. That change in sensitivity would require half the amount of light to get the same exposure.
But you don’t want to compromise the quality of the image with a higher ISO. You decide to change the shutter speed. You need to make the shutter speed longer to offset the reduced brightness. So, you change the shutter speed from 1/125 of a second to 1/60 of a second and you get the same exposure
How It Works with Aperture Priority
If you take the same scenario but this time you are shooting aperture priority, the camera makes the adjustment for you. Here’s how that works…
You have set the shooting mode to aperture priority with an ISO of 100 and an aperture of f/5.6. The camera determines the shutter speed needs to be 1/125 of a second.
When you change the aperture to f/8, the camera adjusts the shutter speed to 1/60 of a second to compensate for the reduce brightness. The exposure does not change.
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Read more:
Tell Me More About Exposure
Tell Me More About ISO
Tell Me More About Aperture
Tell Me More About Shutter Speed
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