What does red eye mean?

"Red eye" generally refers to the phenomenon that when people take pictures, the flash illuminates the human eye and the pupil dilates, resulting in redness of the retina. Because the degree of red-eye phenomenon is determined by the depth of pigment in the subject, if the subject's eyes are darker, the red-eye phenomenon will not be particularly obvious. "Pink eye" also refers to infectious conjunctivitis.

The word "red eye" is actually aimed at the photographer. When the flash illuminates the human eye, the pupil will enlarge to let more light pass through, and the blood vessels in the retina will turn red in the photo. Because the degree of red-eye phenomenon is determined by the depth of pigment in the subject, if the subject's eyes are darker, the red-eye phenomenon will not be particularly obvious.

The phenomenon of human red eye is usually that when shooting in a dark environment, the pupil will expand to let more light pass through, so the blood vessels in the retina in the photo will be dyed red, but for animals, this phenomenon will occur even when shooting in sufficient light. ※.