I just wrote something about digital photography and I realized that I made a few errors. So today I'm going to go over some really basic photography concepts, mostly to get them into my mind so I don't get confused when I use my camera. These concepts are from the books that Dennis Curtin puts out, which are excellent introductions to photography in general and digital photography in particular. I'm only going over a couple of things, read his books to get a lot more than what I writing here.

There are a couple of important concepts to remember. One is light and the other is focus. The amount of light entering the camera determines how bright the resulting picture will be. There are two main lighting controls on most cameras: aperture setting and shutter speed. The bigger the aperture, the more light that gets in, but the smaller the depth of field which affects focus. The faster the shutter speed the less light that gets in, but the less blurry a moving object is.

Shutter speed is usually in fractions of a second: 1 second, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s and so on with an approximately halving of speed between one setting and the next. Now, a professional high speed camera you can get 1/30000s shutter speed, fast enough to photograph race cars sharply at close range. In general 1/60s is considered fast enough for most uses (and is the setting on my camera when you turn on the flash). I find that you want at least 1/15s if the subject is walking or moving slowly, and at that speed it'll be a little blurry.

Aperture is measured in f-stops which is based on focal length. Lower f-stops are larger apertures, letting in more light. My camera has f-stops like f/2.5, f/4, f/7, f/11 so it's not really linear or anything. F-stops are harder to judge, I don't really have a feel for them. In general you want a larger f-stop which makes the picture darker but keeps everything in focus. With a smaller f-stop you can increase the shutter speed to get the same amount of light, but the depth of field decreases (depth of field is the range of distance where objects will be sharp) so it's easier to get an out-of-focus shot which will make the picture blurry too. Whether the picture is blurry because the subject was moving or because it's out of focus doesn't matter, it still looks bad (unless that was the effect you were looking for).

One way to alleviate depth of field problems is to use zoom. The less zoom you have the more depth of field. So with your camera at wide-angle zoom you have a much larger depth of field than if you are at max zoom. So you can make the aperture bigger to get more light and shoot a faster shutter speed to prevent motion blur, then go to wide-angle zoom to compensate for the depth of field so you can keep the subject in focus. The drawback of course is that the subject is smaller. Now, one way to post-process a picture to sharpen it is to reduce the image size. Take a big blurry image and reduce it to 1/4 or 1/16 size and you get a smaller, slightly blurry image. So there's a tradeoff at times when you want to shoot a moving target close up and be blurry (then hope to fix it in post-process) or zoom out to keep it sharper but smaller.

Keep in mind that I've been writing based on my experiences shooting in indoor lighting conditions without flash. If you use flash, if you shoot people who stand still, then you can let the auto features of your camera take care of everything for you and your pictures will come out fine. Personally I don't like the look of flash, it flattens out a picture; and I don't particularly like the staged look of having people stay still smiling at the camera.

So that's it. You have three controls (shutter speed, aperture, zoom) which control three factors (light, focus, size) in varying degrees. Unfortunately photography is like this: you can't change one variable without affecting other variables, so it's a bit of a juggling act to get all the settings correct to shoot the shot you want. That's why automatic cameras are great, but for the most part they do best in good conditions: outdoor, lots of light, portraits. Those are not the kind of conditions that I like to take pictures in, so I have to remember these things when I use my camera.

There are lots of other things I didn't talk about: ISO, exposure, contrast and brightness, lighting conditions, etc. They're are less important than the above three things, and unless you're really into photography it's probably too much work trying to learn their intricacies. It's too much for me at least, I have enough trouble working my camera with only the three controls that I use.