8

I took these photos of two LEDs:

LEDs up close 1

LEDs up close 2

from my Nexus 5 phone. The distance between the lens and the LEDs was lens than 2 cms.

The bands only appear when going up this close.

Are these a software/image processing artifact? Or is this an optical phenomenon?

  • They might be unintentional processing artefacts, but they look pretty nice to me! – Matthew Dresser Oct 23 '15 at 7:16
  • @MatthewDresser Why do you think they were captured unintentionally? ;) – iceman Oct 24 '15 at 13:25
8

This is something specific to photographing LEDs. Most LEDs aren't on all the time, but are in fact flashing extremely rapidly. The ratio of on/off time (the duty cycle) can be used to control the perceived brightness of the LED. The camera you are using has a rolling shutter. When your camera takes a photo, it actually scans the image from top to bottom (or in this case horizontally) over time, rather than taking the whole picture at once*. The process is extremely quick, but in this case still too slow to hide the normally imperceptible flashing.

Your phone is fine and is working normally. It also has nothing to do with the fact that this is a macro shot.

*Cameras which -can- do this are said to have a global shutter. They're very expensive and are used for high-end digital video (movie cameras and the like).

  • An inexpensive film or digital camera with a leaf shutter can also avoid scanning artifacts. – Michael C Oct 18 '15 at 12:51
  • out of interest, what "inexpensive" digital cameras use leaf shutters? I've only used one, and that was a Hasselblad! – Digital Lightcraft Oct 19 '15 at 10:23
  • Usually consumer compacts. Nicer than phones (so not an electronic shutter), but with small sensors and an integral lens so no need for a focal plane shutter. I think my old superzoom (an FZ72) had one. – Jim Oct 19 '15 at 14:32

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