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how can I change the shutter speed of my webcam in Linux?

I'm using fedora 14

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3 Answers 3

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Most webcams, being optimized for capturing video data in a tiny size and budget, don't have shutters at all and thus shutter speed is an irrelevant setting. Really good ones might have some kind of aperture control. Generally they will just use the drivers to set different sensitivities on the capture chip and do post processing to get a reasonably lighted picture.

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While most webcams don't have a physical shutter, they still have an electronic shutter. The effect of this electronic exposure control can be easily seen with qv4l2 or any other application that displays actual video capture frame rate: when a camera doesn't receive enough light, it lengthens exposure, and when exposure time (shutter speed) is greater than inter-frame interval, the webcams decreases the frame rate from 30 to as low as 5 frames per second. If qv4l2 shows 15 fps let it see a bright lamp and the FPS jumps to 30.

I tested 3 cams and all of them exposed this behaviour. One of the 3 has a manual exposure control (3rd tab of qv4l2), and by changing it it's possible to control the webcam shutter speed.

With the other 2 cams I could only control exposure time indirectly by providing enough lighting.

Note that there are 4 distinct ways to make a reasonably bright picture:

  • By post-processing on PC side
  • By controlling video-amp (essentially an in-camera post-processing)
  • By controlling exposure time (electronic or physical)
  • By controlling lens aperture (but most cams don't have an adjustable iris so it's for completeness only)
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If it's possible at all, it depends on the model. It won't be possible with simple, built in webcams.

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