Red-Eye Effect
To conclude the flash topic, you need to know something. You probably have already seen a lot of pictures with people around christmastrees or at night-events with everyone around having red eyes.
Why? Why is everyone's eyes are red? ... Think about it for a second: the back of the human eye (retina) is red. If light is reflected from it, it is seen is red. But how is it that some cameras generate red-eye effect, some dont...? It is because the angle of reflection is too narrow.
With an SLR for example when you fire your flash that sits on a ~8cm high stand on top of your camera and the mount still has another ~3cms from the lenses. That gives you a 2.1°s reflection angle at a subject distance of ~3meters. If you are using a flash of a compact camera that sits right on top of the lenses, having ~2cms distance total, you will get this angle around 0.4°s. This is narrow enough for the light reflected from people's retinas to reach back into the lenses and be captured as: red eye effect.
How to avoid red eye effect? There are two options mainly if you really need to use flash: use an external flash or a camera that has its built-in flash away from the lens more than ~9-10cms.
Or you can still use your camera's red-eye correction feature. This fires the flash 2-3 times but with less power to avoid strong reflectance. Be aware that between the two shots, movements of the subject or the camera can easily happen. This results in motion blur and eliminating some parts of the use of flash. Really a more distant flash-source is the best solution.
Why? Why is everyone's eyes are red? ... Think about it for a second: the back of the human eye (retina) is red. If light is reflected from it, it is seen is red. But how is it that some cameras generate red-eye effect, some dont...? It is because the angle of reflection is too narrow.
With an SLR for example when you fire your flash that sits on a ~8cm high stand on top of your camera and the mount still has another ~3cms from the lenses. That gives you a 2.1°s reflection angle at a subject distance of ~3meters. If you are using a flash of a compact camera that sits right on top of the lenses, having ~2cms distance total, you will get this angle around 0.4°s. This is narrow enough for the light reflected from people's retinas to reach back into the lenses and be captured as: red eye effect.
How to avoid red eye effect? There are two options mainly if you really need to use flash: use an external flash or a camera that has its built-in flash away from the lens more than ~9-10cms.
Or you can still use your camera's red-eye correction feature. This fires the flash 2-3 times but with less power to avoid strong reflectance. Be aware that between the two shots, movements of the subject or the camera can easily happen. This results in motion blur and eliminating some parts of the use of flash. Really a more distant flash-source is the best solution.
The Red-eye effect and after its digital removal
