So, Why Are They Called F-Stops?

I’ll explain — there’s some math involved

Mark Ali
Counter Arts

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The aperture, shutter speed, and ISO settings on a camera
“Aperture” (© Mark Ali)

Most of us photographers are familiar with the concept of aperture. We know what it means, and how it affects our shots.

But, although we throw around terms like “f-stop”, many of us don’t really know why we use that term, or where that number comes from.

I’m going to try to change all that.

First, a disclaimer: Yes, I know that there’s been roughly a gazillion articles about this topic on the internet, in magazines, and elsewhere. This is just my take on it — a ‘brain dump’ of what I know that I hope you’ll find informative. (If you think I got anything wrong, just let me know.)

Firstly, what’s a “stop”?

A “stop” is a unit of exposure, where each added “stop” of light represents a doubling of the light, and each removed “stop” represents a reduction of light by one-half. (I won’t dive into detail about where the term “stop” actually comes from. We’ll leave that for a future article.) Exposure for a given photo can be adjusted by increasing or decreasing shutter speed, aperture, or ISO, and doing that either adds or removes “stops” of light.

Confused yet?

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Mark Ali
Counter Arts

I’m a writer, a photographer, a music lover, and a professional ice sculptor. I’m kidding about that last thing. (View my portfolio at: markaliphotos.com)