Gather round the campfire, photo scouts. I’ll tell you a story. It’s about things that you’ve probably wondered about in your sleeping bags late at night. You all spend a lot of time with numbers. Shutter speeds, apertures, film speeds, and ISO settings are part of the language of photography. We learn them so early that most of us stop thinking about them. A shutter speed of 1/125 second feels natural. So does f/5.6. ISO 400 seems perfectly ordinary. But if you look closely, the numbers are peculiar. The underlying mathematics of exposure is simple. One stop is a factor of two. Double the exposure and you’ve increased exposure by one stop. Halve it and you’ve decreased exposure by one stop. Shutter speeds fit naturally into that framework. The mathematically exact sequence would be 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, and so on. Yet cameras are marked 1/8, 1/15, 1/30, 1/60, 1/125, and 1/250. Somewhere along the way, photographers and manufacturers decided that 125 was friendlier than…
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