Does flash placement on a compact camera really reduce red-eye?
Asked 4/3/2014
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I'm wondering whether the position of the built-in flash on a point-and-shoot camera makes a meaningful difference in reducing red-eye. If the flash is placed a bit farther from the lens, will that noticeably help, or are compact-camera flashes usually still too close to the lens for it to matter? The cameras are only examples; I'm asking about the general principle.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
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It depends on the distance at which the picture is taken. According to Wikipedia:
If direct flash must be used, a good rule of thumb is to separate the flash from the lens by 1/20 of the distance of the camera to the subject. For example, if the subject is 2 meters (6 feet) away, the flash head should be at least 10 cm (4 inches) away from the lens.
2 meters is already pretty close for a portrait shot, and those cameras look like the distance between flash and lens is less than 10cm, so they'll probably still cause red eyes for all but extremely close shots.
To be exact, in order to avoid red eyes, you want the angle of reflection from the flash to the lens via the eye to be more than 2.5 degrees, which means an angular distance of at least 5 degrees:
But nowadays most cameras can emit a pre-flash that causes pupils to contract (reducing the effect) or even automatically remove red eyes in post-processing.
Originally by user25699. Source · Licensed CC BY-SA 4.0
user25699
12y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—flash position matters, but on most compact cameras the built-in flash is still close enough to the lens that red-eye can still occur.
A common rule of thumb is that the flash should be separated from the lens by about 1/20 of the camera-to-subject distance. So if your subject is 2 m away, the flash would ideally be about 10 cm from the lens. Many compact cameras have much less separation than that, so for typical portrait distances they may still produce red-eye.
The reason is geometric: to avoid light reflecting straight back from the subject’s retina into the lens, you want enough angle between the flash and lens. A slightly higher or more offset flash helps, but usually not dramatically on a small camera body.
So the answer is: a farther flash position can reduce red-eye, but among compact cameras the difference is often limited because the flash is still relatively near the lens. Red-eye reduction modes and avoiding direct flash are often more effective.
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