The flash is that little bombillita we have in the vast majority of cameras, including those of our smartphones. As you all know, the main purpose of this light source is allowing us to take pictures when the lighting conditions are not good too, but it is not gold that glitters. Although we can take pictures anywhere is blacked though, we often find that our subjects' eyes appear red, and the explanation for this is as curious as interesting, because it must, quite simply, that we caught our unsuspecting eyes. Fortunately, understanding the reason is really simple and, of course, can be avoided with certain tricks.
The first: how the eye works?
Although we could spend hours talking about how the eye works, what really interests us is to know the basic parts. Roughly, the eye consists of many ribs, one pupil -the black hole, the iris -the color circle surrounding the pupila- and retina -which it is the "collects light sensor"-.
The iris is a curtain which enlarges or shrinks depending on the amount of light to which we are exposed -yes, like the diaphragm of a camera. When there is lots of light, the iris is enlarged, and the pupil becomes a tiny black hole by entering low light. When we are in the dark, the iris opens, and the pupil becomes too large, so that a greater amount of light to pass onto the retina.
Low light, the iris and the pupil shrinks becomes very large / Raziel
Once the light reaches the retina, this "makes" into nerve impulses and sends it to the brain, which converts these impulses into this very simplificado--all images. Obviously, the retina is ready to capture a certain amount of light, and if that amount is exceeded, the light "remaining" must be filtered to produce no damage. Here the red-eye effect.
Red eyes are caused by blood
Within the retina of our eyes there is a layer called semitranspartente pigment epithelium. This layer is responsible for filtering the light that the retina can not process. Inside there are specialized cells in filtering the light "moving light" surplus to an area filled with blood vessels which are full indeed of blood.
These blood vessels are illuminated when the light comes, peeling red color of blood that's inside. The light emitted by the flash is very powerful and momentary, so the iris does not have time to close, the pupil is completely open and the retina receives an immense amount of light that is filtered. In doing so, blood vessels much light and the camera captures the moment to take the picture, and when the effect occurs "Red eyes".
And how can you fix?
Obviously, this is a completely biological effect, so it is almost impossible to avoid it-and we would have to change the functioning of the eye. But that does not mean we can not reduce it. For this, new flashes incorporate a system that, instead of throwing a single flash of light, They emit bursts. That makes the iris become accustomed to the light and closed, which greatly reduces the red-eye effect.
The ancient flashes like the Canon EOS 1100D only emit a flash of light
We can see a lot in mobile phones, which tend to throw three flashes: one for focus, and two very quick serving to illuminate the scene. Flashes professionals who are able to do that are usually quite expensive, but they are increasingly popular.
Obviously, the vast majority of photo editing programs usually come equipped with a red-eye corrector, which is usually as simple as two clicks: one on the tool and another in the eyes -Lightroom, Adobe, it works thus.
However, if you do not have editing programs, no flash art or photography you know, there is a remedy suitable for all audiences. Before getting the photo with flash, stares at a light source: A lamp, a mobile flashlight, car lights ... for a few seconds, and then picture yourself. This will cause the iris is closed to filter the light that reaches the retina and therefore will be closed when the flash light lance, which and even reduce red eye evitará-.