What’s that “f” thing, anyways?

I want to try to explain what some of those crazy little photography settings are that I shove under all of the photos. The “f” thing is called an f-stop, and refers to the size the aperture is when you take a picture. The aperture is the hole in the camera that lets the light in. This light eventually hits your film or plate and there you get your image.

The aperture is adjustable, of course. If it’s a really bright day, you may not want to let all that light in. If it’s dark out, you might want to open it up all the way to let in as much light as possible. Each position you adjust it to is an f-stop. The stop refers to it being a physical setting or adjustment, and the “f” itself, depending who you ask, may either be “focal” or “fractional.” Let’s take that last one. It’s telling.

Each f-stop represents a fraction of space that is in the aperture opening. It’s a fraction of the focal length over the diameter of the opening. Because the numbers could be different from camera to camera as some are big and some are small, the actual size of the aperture may differ, but the ratio of them could remain the same. So the stops on modern cameras are set out to reduce the size of the opening each time, halving the opening each time. It’s like a half-life (if you like science) or the square root of 2 (if you like math).  It’s geometric! Because it’s a square root thing, the numbers aren’t simple fractions and they look a little funny, just remember that with each step, the aperture is cut in half.

So what does that all mean? The larger the f number, the smaller the aperture, the less light gets into your photograph. For quite some time, the smallest f-stop was f/8. The stops would run, from larger aperture to smallest aperture, like this:

f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8

They get much much smaller now, but many cameras still only go down a few small. So now, hopefully when you see the photos of the day, you’ve got a general idea of how much light I’m working with.


~ by glasslajora on February 19, 2010.

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