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Controlling Exposure
 
DaveThomas
Posted: 03 February 2011 02:57 PM   [ Ignore ]
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I see an interesting paper on using multiple video frames to to get a single frame with less blur:

http://www.umiacs.umd.edu/~aagrawal/sig09/index.html

The technique requires varying the exposure on consecutive frames.

Is this possible with CL-Eye driver?

Separately, but related—-

I’ve been thinking I need high frame rates to reduce motion blur of fast moving objects.  I realize that the trade-off will include reduced exposure times, and therefore either darker video or more ambient light required.

However, thinking more (always dangerous), mabye higher frame rate is just a means to an end and I could accomplish the same thing by just using exposure?

Can exposure (aperature open time) be set less than the period of an entire frame?  What’s the minimum time for the PS3Eye?

Thanks,

Dave Thomas

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thesmileman
Posted: 03 February 2011 03:26 PM   [ Ignore ]   [ # 1 ]
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Yes it is possible.

Have you read the API reference?

http://codelaboratories.com/research/view/cl-eye-muticamera-api

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DaveThomas
Posted: 03 February 2011 03:44 PM   [ Ignore ]   [ # 2 ]
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Yes, I read that, but can the exposure be changed on a frame by frame basis? 

For example, if I capture a frame, then make the call to change exposure, will the exposure get set in the camera in time for the next frame?  Or a fixed lag in # of frames?  (probably not, I’d guess).

Also, not sure about the units 0-511.  I saw something about rolling exposure and this is the number of lines.  But, it’s still not clear to me.

Can someone point me to something that explains what the exposure setting really does in the camera?

Thanks,

Dave Thomas

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thesmileman
Posted: 03 February 2011 09:14 PM   [ Ignore ]   [ # 3 ]
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I see your point.

Just wrote a quick test and you can do it every frame (Color me surprised as I didn’t think this would work) at least a 30fps but I don’t know why you couldn’t do it any faster I just tested it at that fps.

I think it is simply a range for which the exposure of the camera can be set.

It is pretty simple to try yourself:

boolean swapExposure = true;
private CameraFrame getNewCameraFrameBuffer() {
    camera.setCameraParam(CLCamera.CLEYE_EXPOSURE, swapExposure ? 3 : 500);
    camera.getCameraFrame(frame.data, 0);
    swapExposure = !swapExposure;
} 
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DaveThomas
Posted: 04 February 2011 02:45 AM   [ Ignore ]   [ # 4 ]
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So, how did you tell the exposure was actually getting set each frame?

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DaveThomas
Posted: 04 February 2011 08:20 AM   [ Ignore ]   [ # 5 ]
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wrt rolling shutter, found this:

http://www.appliedcolorscience.com/rolling_shutter_image_sensors.htm

Helped me a lot.

Dave Thomas

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thesmileman
Posted: 04 February 2011 10:11 AM   [ Ignore ]   [ # 6 ]
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DaveThomas - 04 February 2011 02:45 AM

So, how did you tell the exposure was actually getting set each frame?

You can see in my code I swapped between 3 and 500. Basically at “3” you could see everything and at “500” and you could only see my recessed lights and everything else was black (Maybe that is revered I but you get my point).

You should try this yourself.

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