What is Exposure Triangle and how does it relate to Aperture, Shutter and ISO?

What is exposure triangle?

To put it simply, it’s a method or analogy ‘gurus’ use to initiate noob photographers and cinematographers into the ways of the aperture, shutter and ISO. Sort of like a right of passage that you are compelled to continue perpetrating on new entrants.

I’ll tell you, I gave up photography for a couple of years after hearing this explanation. Here’s my quick and easy explanation of the exposure triangle, and how it relates to aperture, shutter and ISO:

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What is the exposure triangle?

The exposure triangle isn’t really a triangle at all. It’s just a way of saying the aperture, shutter and ISO are all related to each other.

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 in a circular fashion, hence letting more or less light in – just the way you want it.

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.

What is shutter?

A shutter is a second aperture, but in addition to blocking light, it does so with a timer on. You decide how much time the shutter stays open.

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
  • The shutter controls motion blur or sharpness

Both are creative tools more than physical ones. There’s nothing stopping tomorrow’s technology from combining both into one system.

The primary creative job of a photographer and cinematographer is the manipulation of aperture and shutter to get the effect he or she desires.

What is ISO and why do we need it?

The video does a good job of explaining ISO with an analogy. Just to add to it:

ISO is like a buffer, a safety net.

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.

Summary

That’s the exposure triangle for you – 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.

Exclusive Bonus: Download my free guide (with examples) on how to find the best camera angles for dialogue scenes when your mind goes blank.