Principal Flash Limitations
While flash is the all-purpose light source that will work in many situations, it does have plenty of drawbacks. Never take a flash shot and expect it to be perfect unless you have had a lot of experience. Flash can get very technical, but it allows you full control over lighting.
Typically, when shooting indoors, the flash will work adequately if the subject you're shooting is within ten to twelve feet. Beyond that you may be out of luck. However, when zooming in on a subject more than twelve feet away, some sophisticated flashes will zoom with the lens so that the light will go farther and be more concentrated. Most flashes are designed to cover a normal lens angle of view, so if your zoom is set to wide-angle you may find that the edges will not get lit properly.
Flash pictures often look a bit staged due to the directionality of the lighting and the harshness of it. Since most cameras have an on-camera flash mounted on the top of the camera, flash produces a severe lighting, much like having the sun directly behind you. Pictures taken with an on-camera flash tend to look similar, since the flash produces a flat light that minimizes surface textures. There are several solutions to this problem. For example, a dedicated bounce flash or an external flash that is moved to the side solves this problem.
Direct on-camera flash of people often produces an effect that is called red-eye. When a person's eye is open in low light, the flash reflects off the retina and produces a horror-movie red-eye look. The solution is to use the red-eye reduction flash setting, to not have the subjects look directly into the camera, to move the flash off the camera, or to bounce the flash.
Some people put a white handkerchief over the flash to soften the light. While this works well in close shots, it reduces the power of the flash so that it does not work in all situations. Also make sure that the fabric is really white, as the flash will take on the color of the cloth.
The bad news is that red-eye reduction is not always totally successful. The good news is that if your subject does end up with red eyes, you can correct the problem with image-editing software. If you do a lot of portrait work, you will want to buy an auxiliary flash that, when used properly, will not produce red-eye.
Red-eye occurs because most flashes are on axis with the lens. This means that the flash and lens are lined up together. When the flash fires, the light enters a person's eye and bounces around, taking on a reddish tint before coming back directly to the lens. If you move the flash off axis you will generally get rid of the problem.
Everyone has seen flash shots, where people blinked and it looked as if their eyes were shut. You will not be aware that a person has blinked because you cannot see the picture when the flash fires on the LCD monitor, although you can see it through an optical viewfinder.
