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I'm not talking about photography in this question, I hope not to be in the wrong place but I think here someone can give me good ideas.

I'm working on some videos for computer vision tasks. The videos are taken with a video surveillance camera (I can't change the exposure). Sometimes I have problem problems of overexposure: some part of the image are super-bright.

Even if I'm handling the problem in the image-processing/digital side to correct it, I'm still curious if there are some analogical filter I can apply on to the lens to correct the overexposure.

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closed as off-topic by mattdm, Paul Cezanne, AJ Henderson, MikeW, Michael Clark Jul 29 '13 at 23:23

  • This question does not appear to be about photography within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

    
Signal Processing Stack Exchange dsp.stackexchange.com –  mattdm Jul 29 '13 at 13:13
4  
This question appears to be off-topic because it is about computer vision, video, and signal processing. –  mattdm Jul 29 '13 at 13:13
3  
You could try using an ND filter on your lens, although I doubt there are off the shelf ND filters for surveillance cameras. –  Bart Arondson Jul 29 '13 at 13:32
1  
@mattdm would be better migrated to avp.stackexchange.com rather than dsp.stackexchange.com –  Matt Grum Jul 29 '13 at 14:04
    
@MattGrum Yeah maybe, particularly if it's all about handling the overexposure. –  mattdm Jul 29 '13 at 14:15

1 Answer 1

up vote 4 down vote accepted

You are looking for an ND filter or neutral density filter. It's effectively sunglasses for a camera. You can get them with a certain number of stops of power (ie, how many times it halves the light transmitted).

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