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#1 |
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Hi all,
Do camera sensors interpret infra-red as red? I saw a picture taken, which had had it's IR block filter removed, and a -850nm block filter installed, and the images had a red cast. Why is that? Thanks, ..... john |
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#2 |
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If a camera has had its IR Blocking Filter removed, but not its Bayer Filter, and an IR Passing Filter installed, the only light to get passed the IR Passing filter is IR , and possibly some red light. The Green and Blue microfilters in the Bayer filter would block the Red/IR light, so the only photoreceptors that would detect any light would be the ones under the Red microfilters. The camera would interpret that as red light on an otherwise black background, because all other wavelengths of light were blocked.
That sounds like what you described.
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#3 |
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Hi TCav,
Yes, alright, thanks. I think I understand. So .... Does that mean, in modifying a colour digital camera to get a pure NIR image, I would have to remove the IR block filter, the Bayer filter, and install a colour block filter? ..... john P.S. Where is the Bayer filter in most cameras? Last edited by Shinnen; Feb 13, 2016 at 7:58 PM. Reason: remove redundancy |
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#4 | |
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#5 |
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If I were going to do this for a serious application, I think I'd choose a camera with a Foveon sensor or a camera with a monochrome sensor. Either would produce a B&W image of an IR scene, instead of an image with a false tint.
See Sigma SD1 and SD15 for Digital Infrared Photography or David English: Infrared Monochrom.
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#6 |
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Hi Tcav,
Alright. So, that's a black and white sensor, as opposed to a colour camera with black and white capability? Thanks, ..... john |
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#7 | |
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A monochrome camera will always be a monochrome camera.
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#8 |
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Hi Tcav,
I see now why you said "serious application" These monochrome cameras are expensive. I read this http://www.digitalphotopro.com/gear/...chrome-capture article, which helped me to understand. But, no, I'm not going to spend this kind of money. If I understand him correctly, he implies that the monochrome setting on a colour camera will produce a monochrome image (qualitatively) but will not quantitatively produce an accurate image, due to the various filters which change the intensity of the light reaching the sensor?? ..... john Thanks, ...... john |
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#9 |
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The key things are to remove the IR Blocking filter, and install an IR Passing Filter.
Whatever happens after that, you can play with however you want, because all you'll capture is IR. Whether it shows up in the image as white, red, or green, is immaterial, because IR is none of those colors. Whatever color you get will be a false color.
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#10 |
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Hi Tcav,
It's my impression that pure NIR images are colourless, i.e. shades of black and white. Is this also false "colour" i.e. just a colourless manifestation of IR, not any 'purer' than the coloured ones? .... john |
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