Here’s What Your Camera Does When You Change ISO & Why Higher ISO Creates Noise
I can’t speak for anyone but myself here, but I would imagine I’m not alone when I say I’m always fascinated by, and eager to understand, the things we all use in everyday life and really don’t quite know how they function. A basic example would be how a car works. We use them all day every day and yet many people haven’t the foggiest idea of what’s actually going on within the innards of the car, the parts you can’t see, to make it go. There’s a lot that’s going on regarding the sequence of events that occur when the gas pedal is depressed.
Similarly, in photography, so many of the basics that we use day in day out, go misunderstood. Or, if not misunderstood, there’s no real thorough comprehension of how it works, other than how it affects our ultimate exposure. ISO, in today’s age, is one such facet. Sure, most know how to manipulate ISO and balance it with shutter speed, aperture etc, to end up with a desired exposure result, and we know that raising the ISO will generate noise in our image, but do we know why?
Ian Gibbons of Panvista Productions put out a video a while back which does a nice simplistic overview of how ISO really works behind the scenes, and thus, how it affects exposure, what the camera is thinking and doing when you raise or lower it, and why we get ‘noise’ from digital ISO changes. It’s quite fascinating stuff, and I’m not ashamed to admit I hadn’t known before that it was electrical interference that causes noise. It’s all a somewhat simplistic overview, but a good one regardless.