Lesson #5: Putting it all together

So far you’ve learned that aperture controls your depth of field. And you’ve learned that shutter speed controls motion blur. And you’ve also seen what ISO does to your pictures.

Here’s where we put it all together. All photography is simply a balancing of those three things. They are all interrelated. Old-tyme film cameras only allowed you to choose full stop settings when choosing your aperture and shutter speed. And for simplicity’s sake, I’m going to give you the next examples in full-stop numbers.

Here’s a list of full-stop apertures:
1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32.
Here’s a list of full-stop shutter speeds:
1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000.
Full-stop ISO settings are:
100, 200, 400, 800, 1600, 3200, 6400.

So, for example, say you’re out on a bright sunny day. Using ISO 100 you get an exposure reading of 1/125th of a second at f/16. If you dial down one f-stop aperture -- to f/8 -- you’ll have to dial up one f-stop of shutter speed -- to 1/250th -- otherwise your photo’s going to be overexposed. See how that works? If you open up your aperture three stops, then you’ve got to increase your shutter speed three stops.

It’s the same for ISO. If you increase your ISO one stop, you have to reduce either your shutter speed or aperture (your choice) by one stop.

And that’s where the creativity really starts to come into play. As the photographer you have to decide what settings to use. Yes, modern cameras are awful good at deciding for you. But to be truly successful as a photographer you have to understand what the camera is doing, and you have to know when to override the camera, in order to get the results that you want (or need, as the case may be, if you start trying to make money with your camera).

So when you sit down to take a photograph the thought process starts:

Do you want lots of depth of field (for a landscape)? Or do you want little depth of field (for a portrait, to throw the background out of focus and keep the subject the focus of the photo)?

On to shutter speed, is the subject moving? If not, you can almost forget about shutter speed (if you have a tripod anyway). If it is, do you want a little blur in the photo, or do you want it frozen tack sharp?

Then on to ISO, do you want a noise free image that is very high in quality. Or is a little noise (grain if you’re a film shooter) okay in this image? Or (in case you’re really getting artsy) do you want excessive grain for a special look?

You’ve got to put all those elements together and come out with a compromise between all three to make the image that you want.

Next lesson!