There are also disadvantages when using the flash. For example, when shooting a person, the light of the flash may remain in the pupil of the eye, and then a "red-eye" situation occurs. Therefore, many camera manufacturers have added the "red-eye removal" feature to their designs. Before the flash is turned on, shoot a dim light to adjust the pupil, and then execute a real flash to avoid red eyes. Mid-range and low-end digital cameras generally have three flash modes, namely auto flash, red-eye reduction and flash off. More advanced products also provide "forced flash" and even "slow flash" functions.