Prefocusing or Focus Lock
Most automatic focus systems focus on the center of the picture. Usually there is a mark in the center of the viewfinder to show where the camera is focusing. However, sometimes your focal point may not be in the center of the frame. You may want to place the main subject off-center to make the composition more interesting or you may have two friends standing side-by-side with a distant background between them in the center of the frame.
To prevent your subject from being out of focus, you will need to activate the Prefocus or Focus Lock. Center the camera on one of the subjects and push the shutter halfway down. You are telling the camera where you want it to be focused. Next, without lifting your finger, move the camera back to reframe your photo and press the shutter the rest of the way down.
If you have a digital camera, you can check the picture in Playback mode.
Cameras with automatic exposure can be confused by strong backlighting. Since the camera adjusts automatically for the best overall exposure, your subject may be dark or underexposed if the strong light is in the back. Move your subject to adjust the direction of the light.
Most cameras come with a built-in flash. The job of the flash is to provide extra light so there is enough light to get the picture. In some cameras, the flash will flash for every photo you take. In other cameras, it will automatically turn on when the camera senses the flash is needed.
Some digital cameras have special flash modes such as autoflash, red-eye reduction flash, fill-flash, night flash and flash off. The red-eye reduction flash mode causes a bright lamp or series of flashes to go off before you actually take the picture. Look at your camera manual.
Know how to make your flash work for you.