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#1 Sethoroth999  Icon User is offline

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Is there ANY way to change camera exposure from a beagle bone on linux

Posted 08 February 2013 - 10:44 PM

I need help setting the exposure on any UVC(USB Video Class) type webcam from a beagle board running linux Angstrom .
-V4L2 (video for linux 2) is a driver we've been using (Any alternate will work
- OpenCV is the vision library we're using.

We've been looking for a work around to this for around a month and have searched a plethora of sites (listing them would not help you).
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Replies To: Is there ANY way to change camera exposure from a beagle bone on linux

#2 tlhIn`toq  Icon User is offline

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Re: Is there ANY way to change camera exposure from a beagle bone on linux

Posted 09 February 2013 - 07:45 AM

So many webcams are auto adjusting that it may not even be possible in the hardware. Webcams are little $20 consumer throw away devices these days. The makers don't invest money in making a good API with lots of control over them. If the manufacturer's demo software doesn't do it, then its unlikely you will without finding a way to hack the firmware.

The closest I've seen is a couple iPhone applications that 'lock' the exposure when the user presses a button. But the camera is still auto-adjusting. So you manipulate it by covering the lens so it goes full-open-exposure then starts self-adjusting darker - then you quickly lock it where you want. Its a hack and its one-time use: You can't save and restore that setting.

The simple truth is if you want control of a camera, a webcam is the wrong hardware choice. A Canon or Nikon with a developer SDK is the direction you need to go.
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#3 Skydiver  Icon User is offline

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Re: Is there ANY way to change camera exposure from a beagle bone on linux

Posted 09 February 2013 - 08:20 AM

Listen to tlhIn`toq's advice. He makes a living taking pictures via computer control.
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#4 tlhIn`toq  Icon User is offline

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Re: Is there ANY way to change camera exposure from a beagle bone on linux

Posted 09 February 2013 - 09:27 AM

Thanks. But to be fair I don't do it in *nix. And there are a lot of uses for webcams beyond what I do. ID card photos, chat applications, motion detection and so on.

We use one strictly as a light meter. Its hardware lets you turn off auto-adjust. It can then be pointed at a neutral grey wall outdoors. Being a known value in sunlight we can look at the histogram of the image and determine the brightness. Then tell the good camera to change settings. Its a ton cheaper than a light meter with connectivity and an API.

But that requires hardware with certain capabilities. The OP wants to have fine adjust over settings with ANY usb webcam and that simply isn't going to happen.

The fact that they dumped a month of labor into a project without first checking if its even possible with the hardware or writing the hardware manufacturer stuns me.
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