Everybody knows the exposure triangle by now, right? ISO, aperture and shutter speed. Once you know your scene’s exposure value, you can just balance out the three to get a good exposure. And as you adjust one up or down, you need to adjust another in the opposite direction to compensate. Well, what if one of them isn’t really anything to do with exposure?
That’s the argument put forth by Chris Lee of the YouTube channel pal2tech, and it’s a compelling one. Back in the days of film, it was a little different, and your ISO really did reflect the sensitivity of the film stock to light. These days, though, with digital cameras, not so much.