You’ve probably encountered the red-eye effect on photographs at least once in your lifetime. But when trying to fix the colour with image editing software, have you ever asked yourself the question: Why? Why does this effect occur?
The lens of a camera admits a huge amount of light into the eye in a very short time. Since the retinas have rich blood vessels, they appear later on the photograph as red eyes, meaning the red eyes on the photo are actually blood.
For many centuries photographers have struggled with the effect of the red eyes before modern techniques and technology made the red-eye reducing flash possible. One simple way to avoid the effect was to step back from the subject or to use daylight and switch off the camera’s flash. However, reducing the red-eye effect wasn’t always easy, especially with people who had blue or pale eyes. The paler the colour, the more easy it becomes for blood vessels to appear on the final photograph.