It’s easy to blame your equipment when it takes an improper exposure. But a camera is an unthinking, unfeeling machine. It doesn’t know if a scene is too dark or too light, nor does it care. It takes in information about what’s coming through the lens and then adjusts the camera’s settings to set algorithms.
Most cameras are set to expose for an overall average, meaning that they average out all the values of a scene from light to dark. If a background or foreground is too light or dark, it can affect the overall exposure of the photo.
A snowy scene, for example, is mostly white, but the camera will think the overall scene is too bright and will try to compensate by adjusting the settings to make things darker. The result is snow that will be grey and muddy.
On the other hand, something like a concert will usually have a performer on stage illuminated by a spotlight with the rest of the stage fading off into unlit blackness. The camera will see that as a scene that is too dark and the camera will compensate in the other direction and the performer will glow almost radioactively in his/her overexposure.
Most cameras will have three main auto exposure modes: Shutter priority, where you set the shutter speed and the camera sets the aperture; Aperture priority, where you set the aperture and the camera sets the shutter speed; And, finally, Programmed mode, where the camera sets both the shutter speed and aperture. When auto exposure cameras first became popular about 30 years or so ago, they could easily be fooled. Today’s latest cameras are much more sophisticated and are better than those old cameras, they aren’t perfect and still can be duped.
This is why shooting manually comes in handy. I know, most people think setting their own aperture and shutter speed is complicated, and they don’t want to mess with them. And in the old days of film, when you had to wait hours, days or even weeks to get your pictures back from the photo finisher, it could be frustrating learning how to operate your camera on your own because of that wait time. It was difficult to remember what you did right or wrong back when you took the photo. It was easier to have something that was over/under exposed (and blame the camera) than to muck with the arcane business of manual exposures.
But with today’s digital cameras, shooting manually is easier than ever. Sure, you have to fiddle with the camera’s controls, but nowadays you can instantly review the picture that you just shot on the monitor on the back of your camera. (Instant gratification is a wonderful thing.) Then you can stop your lens down/increase the shutter speed if the scene is too bright, or open up the aperture/decrease the shutter if it’s too dark. Unless the light changes, you can just leave the settings where they are and shoot away.
There are compensative settings that many cameras have, including some point-and-shoot ones, but they, too, involve either pressing certain buttons or going into the camera’s menu and choosing them, so you may as well choose manual and have complete control of your camera’s exposure. It takes a little while to master, but once you get the hang of it you can fine tune your exposures in a way you couldn’t before.
It’s sort of like driving your car or taking the bus. If you take the bus, it may take you close to where you’re going but probably not exactly where you want, and you have to confer with the bus schedules to see what time a bus will be coming by. If you’re driving, you can go directly to your destination exactly when you want to. It’s a matter of control. When shooting with manual exposures, the brains of the operation would be you, and not some unthinking machine.