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Thread: Coloured filters and the bayer array

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    Coloured filters and the bayer array

    Hi i am new to this site and have some questions for any experts out there. What i am trying to find out is how a digital camera reacts specifically in relation to the bayer array when a specific coloured light say at a specific wavelength ie 700nm which would be red. What does the bayer array do when only red light hits it as it is the only colour it cannot sense blue or green what are the problems with this how can it be fixed. This is specific for a forensic type situation, as the bayer array would normally be used to some form of white light etc which contains all wavelengths in normal photography. In forensics we use filters to get specific wavelengths before the light eneters the camera and then it hits the bayer array. Does anyone have any clue on this complicated question?
    Thanks Dean

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    Re: Coloured filters and the bayer array

    Hi Dean,

    I understand what your asking, but I don't understand why you feel it might be a problem.

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    Moderator Dave Humphries's Avatar
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    Re: Coloured filters and the bayer array

    Hi Dean,

    I agree with Colin.

    There will be no output from the other bayer elements (G and B), other than noise, so as long as there is sufficient illumination at 700nm, it shouldn't be a huge problem.

    Cheers,

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    Re: Coloured filters and the bayer array

    Well i think the resolution will be bad because the camera is only using 1 quarter of its pixels, hence a 10 megapixel camera won't resolve this at 10 megapixels with only the red pixels sensing the wavelength and the others doing nothing. The cameras are used to sensing electromagnetic radiation at each photsite, with specific wavelengths when using interference filteres this is not the case 75% can be doing nothing, this will create noise and problems with interpolation, and low resolution.

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    Re: Coloured filters and the bayer array

    I'd be inclined to test it and see - at the end of the day it's probably going to depend on how good a job the RAW converter does. I can see what you're getting at, but with any image, the demosaicing algorithm looks at surrounding pixels and tries to decide what the correct colour is supposed to be (and introducing a degree of unsharpness in the process) ... so in other words two-thirds of the colour information is made up anyway, and that doesn't change with what you're doing.

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    Moderator Dave Humphries's Avatar
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    Re: Coloured filters and the bayer array

    With mono-chromatic light, there's not going to be any meaningful colour anyway, at least nothing you couldn't re-create in a PP package if you knew the wavelength it was shot at.

    I'm sure the commercially available cameras attached to these 'scopes use a monochrome camera style sensor, so no bayer array or lack of resolution to worry about.

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