Additional Flash Limitations
Unfortunately there are even more problems with flash lighting. To be able to control this lighting effectively, you need to know all the things that can go wrong.
Because flash is close to some things and farther away from others, you many find brightly lit or overexposed areas close to the camera. These are often called hot spots. The solution is to make sure that there is no piece of furniture or a plant or anything else between you and the subject of the photograph.
Experienced photographers use one eye, such as the right eye, to compose the scene with the viewfinder and then switch to the other eye, such as the left eye, to monitor the scene when the flash fires. They do this because many camera viewfinders, such as LCD monitors and those on DSLRs, black-out just as the shot is taken. To see the effect of the flash, photographers must look at the scene with their naked eye.
When you are taking a photo of a scene with multiple subjects at different distances from the camera, the exposure cannot be correct for all of the subjects. Usually those closest to the camera will be properly exposed. The farther the subjects are from the camera, the darker they will appear in the picture.
Flash requires a lot of electricity. The more powerful the flash, the more juice it will use. Taking nonstop flash pictures will run through your batteries much faster than photographing in available light. If you do a lot of flash photography, make sure that you carry plenty of extra batteries.
Flash stores electricity and then releases it in one powerful burst. Most flashes can take a while to recharge — ten seconds or more — so rapid sequential shooting is not possible with flash. Some flashes will fire before they are fully charged, which will result in underexposed pictures. You should always wait for the flash ready light to come on before taking the next shot.
High-end DSLR cameras use a focal plane shutter. Most of these shutters have a maximum shutter speed that can be used with a flash. For very technical reasons, at faster shutter speeds the shutter curtain gets in the way of the picture and only a portion of the frame will be exposed.
Since it is so easy to review shots with the LCD monitor, it is a good idea to review all your flash shots immediately after taking them. If you have a group of people together, don't let them go until you are certain that you got the shots you want; getting them together later may be difficult or impossible.
