Flash photography has its own special group of problems. Some of the most common problems and their solutions are listed here.
“Red-eye.” This is probably the most common problem with flash photography. It is caused by the close proximity of the flashgun to the lens. The best solution is to get the flashgun off the camera so the light path from the flashgun to the eyes and back to the lens is not a straight line. However, many cameras have the flashgun permanently attached to the camera so it cannot be moved. The solution to this situation is to reduce the size of the subject’s pupils, which can be accomplished by asking the subject to stare at a bright light just before taking the picture. Some cameras have a “red-eye reduction” feature which fires a “pre-flash” before the picture is taken. This does not always eliminate the problem, but it helps. As a last resort, your photo supplier has a “red-eye pencil” which can be used to manually color over the red eye effect.
Underexposed (dark) or overexposed (washed out) flash photos. Each flashgun gives proper exposure only within a certain range of distances. Get too far away and your subject will be dark (underexposed). Get too close and your subject will be washed out (overexposed). Experiment and keep notes to determine the best distances for your equipment.
Multiple subjects unequally exposed. You may have taken flash pictures which have more than one subject, such as a group of people. Some of the subjects may be overexposed while others are underexposed. The way to avoid this effect is to make sure that all subjects are positioned at the same distance from the flashgun. If your flashgun has bounce capabilities, you may bounce the flash off the ceiling or a reflector. This will diffuse the light and spread it out more evenly than direct flash. You will have to compensate for the fact that the reflective substance will absorb some of the light. Also, if the ceiling or reflector is some color other than white, the flash may reflect that color in your picture. Experiment and make notes to determine the best flash to subject distance.
Unwanted reflections. Watch the background for glass such as a window or a mirror which might reflect the flash back into the lens. Shoot the picture at an angle to the glass so the light will not be reflected straight back to the camera.
Overall blue cast. Most color films are balanced for the color of daytime sunlight. Electronic flash is bluer than daylight and will sometimes show an overall blue cast in your photos. The way to avoid this is to use an ultraviolet (UV) filter, which will absorb the ultraviolet light and eliminate the blue cast.
Unnecessary use of flash. You see it all the time at sports arenas. Flashes are going off all over the stadium. Many photographers seem to be unaware that their flashguns are only effective up to about twelve feet. This doesn’t really hurt anything, but it doesn’t help anything either. It just wastes battery power. The stadium lights are generally bright enough to get an acceptable picture.
Failure to use fill-in flash. Many people are unaware that they can greatly improve outdoor pictures of people by using fill-in flash. In fact, the brighter the sunlight, the more you need your flashgun. This is because the sun tends to cast shadows across the faces of your subjects. The film is not able to handle the contrast created by this brightness range. Flash can fill in these shadows and create a more pleasing effect.
Shutter speed – flash sync failure. The flashgun must fire when the shutter is completely open. For cameras with between the lens shutters this is not a problem because they synchronize properly at all shutter speeds. However, the situation is different for single-lens-reflex (SLR) cameras. The shutter of an SLR is a curtain located just in front of the film plane. This is called a focal plane shutter. The shutter speed is not determined by changing the speed at which the curtain moves across the film plane, but by varying the width of a slit in the curtain. The flash from an electronic flashgun is very brief, lasting only about 1/1000 or 1/2000 second. Focal plane shutters are not completely open at all shutter speeds, which means that flash will not synchronize at all shutter speeds. The shutter must be set to a speed at which the slit in the curtain is completely open. This is usually 1/60 second or slower, although some cameras will synchronize at shutter speeds of up to 1/125 or 1/250 second. See your camera’s manual to determine the proper flash synchronization speed (called “X sync”) for your camera. If you use a faster than indicated shutter speed, you will only get part of a picture because the shutter curtain is only partially open when your flashgun fires. It is okay to use a slower shutter speed than the recommended X-sync speed because the shutter is completely open at X-sync speed and all speeds slower and will synchronize properly.
NOTE: If you want to use fill-in flash outdoors with an SLR you may have to use a neutral density filter or a very slow-speed film in order to be able to use an acceptably slow shutter speed.
NOTE: Some cameras use a “dedicated” flashgun which will set the proper X-sync speed automatically. Also, these flashguns give the proper exposure by reading the light which strikes the film plane. There are some newer flashguns dedicated to certain cameras which give a rapid series of flashes (so fast your eye sees them as a single flash) which continuously flash during the entire time the shutter curtain travels across the film plane. These (expensive!) flashguns overcome the synchronization problems of focal plane shutters. They will synchronize properly at all shutter speeds – even 1/2000 second.
ONE LAST NOTE about flash synchronization. Any camera will synchronize properly with any flashgun at a shutter speed of 1/30 second or slower. Use this shutter speed when in doubt.
This report is not intended to be a complete treatise on the use of flash. These are the most common problems. Practice the procedures listed here and notice the improvement in your flash pictures.