What is the formation mechanism of red eye in figure photography?

Red eye is related to flash. Red eye is actually the reflection of flash on the retina. Because human blood is red, so is the reflected light. The function of red-eye reduction is to narrow the pupil and reduce the reflection by passing the multiflash once before the formal flash. Of course, contraction is limited and cannot be completely avoided. If the shooting angle occurs, it is normal that the photos taken have no red eye at all. Under normal circumstances, this function should be turned on, but the disadvantage is that power consumption is more harmful because of pre-flashing. (Consumer cameras only)

Use the reference flash:/star1024/blog/item/ff0b15df87bed3136327981e.html.