Exposure Triangle

Not much brings out pedantic dickheads like a discussion regarding the so called exposure triangle. Wait, did I use the term “dickheads”? Yes, I did. And I mean it. For an example of what I’m talking about go read this at PetaPixel. It’s a great article that explains the exposure triangle and how it’s a tool to demonstrate three aspects of exposure in digital photography; shutter speed, aperture size and, yes, ISO.

After reading the article, if you peruse through the comments, you’ll begin to see what I’m talking about with comments like:

There is a very good reason to hate the triangle. It not only confuses people but its pure nonsense. ISO is not part of exposure. ISO is only applied after the exposure.

Increasing ISO reduces noise in most cases

No. Changing ISO does not change sensitivity.

This guy is actually saying that ISO plays no part of exposure.

That’s just simply incorrect.

Tony Northrup chimed in as well with:

Came here to say this. Great article, but I hate the triangle metaphor. It only confuses people.

Tony Northrup sort of has a point with regards to how this guy presents the exposure triangle, but generally speaking, for people just starting with digital photography, the exposure triangle is a rock solid way of understanding how exposure works vis a vis digital photography. By the way, if you’re starting out, perusing his site would be advisable. He and his wife Chelsea do a very good job of presenting helpful information.

You can visit just about any photography forum and when the subject of ISO and exposure comes up; especially when incorporating the exposure triangle, the dickheads come out en mass to bray that ISO has NOTHING to do with exposure.

Bullshit. If you hear someone say that, disregard them. They are incorrect. They are wrong. They are being pedantic dickheads.

Hell, even Nikon’s website says otherwise:

Aperture + Shutter Speed + ISO = Exposure

The three variables that make up a photographic exposure are shutter speed (how much time it takes to make the exposure), aperture (how big the hole is that lets light through the lens, and into the camera) and ISO (how sensitive the digital image sensor or film is to light).

Now, technically speaking, ISO may not be exposure. A lot of the pedantic dickheads will point out that exposure is the amount of time and light that is allowed to make contact with the sensor. So what. For all practical purposes, in the real world, exposure results in how the image will look; darker or brighter. That is determined by aperture size, shutter speed and ISO. Period. End. Of. Story. Don’t believe me? Try the following.

Get out your camera and set it on a tripod. Adjust the settings for optimal exposure. First set your ISO for, say 400. Perhaps your optimal exposure is then 1/250 f4.5 and the ISO has been set to 400. Take the pic. Look at it. It’s probably pretty close to optimal if your in camera meter shows the little mark at 0. Now, leave everything the same, but this time drop the ISO down to 100. Look at the camera’s internal meter. You’ll see that it is now left of 0; optimal exposure. Take a pic and look at it. You’ll notice that it’s underexposed compared to the first one. Now, do the same thing, but this time bump up the ISO to, say, 1600. You’ll see that the internal meter will show the little dot way to the right, and the resulting picture will be much brighter.

Furthermore, if you set it back to optimal, you can then increase the shutter speed and you’ll notice that the little meter dot is displaying an underexposed setting. You can then bump up your ISO to get the little dot back to 0. You can even take a pic if you like and verify it. You can do the same thing with the aperture as well.

The bottom line is that exposure is comprised of three variables: Shutter speed, aperture size AND ISO in every practical sense. This is why the “triangle” is such a good way to present it. If you make an adjustment to one you HAVE to make an adjustment to one of the other two (if your goal is to be close to optimal exposure). When some pedantic dickhead brays that ISO has NOTHING to do with exposure, then don’t believe your lying eyes. Do the steps above and you’ll see otherwise.

To address the pedantic nonsense that “technically” speaking, exposure is only the amount of time and amount of light coming in contact with the sensor, lets use this metaphor:

Many decades ago, in the US, we stopped using the gold standard. What this means is that our paper and minted money is no longer backed by gold. It used to be that gold was the thing of value that the paper and minted money represented. Without it, it was just paper and metal. Since the paper and metal is no longer backed by gold, technically speaking that crisp $20 bill in my wallet has no real value. It’s simply just paper, cloth and ink. Technically speaking it has no real value.

Except it does. If I can use it to purchase goods of value it has value even if technically it’s nothing more than paper, cloth and ink.

The same applies to ISO. It absolutely plays a part in how bright or dark (among other things) your image is. For all practical purposes, that is going to be interpreted as exposure.

So, who are you going to believe, some pedantic dickhead or your lying eyes and what every digital camera manufacture says?

The exposure triangle. Learn it, know it and embrace it.

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