1 Topic by Adam

  • Adam
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Topic: Spectral lines emulation

I wonder if there is a way in the IA to emulate a light source with accentuated spectral lines.

For example, an image was taken under a direct sunlight with a continuous spectrum and I want to distort it to look like taken under a high pressure sodium lamp.

http://en.wikipedia.org/wiki/File:High_ … ectrum.jpg
http://en.wikipedia.org/wiki/File:Mercu … ectrum.jpg

Thanks.

2 Reply by mv

  • mv
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  • Registered: 2003-09-17
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Re: Spectral lines emulation

Hi
I'm not really sure how that should be done correctly, except for probably making it more reddish...
Under Saturation and vibrance   you can adjust the White balance slider to the left to give it a red tone, but of course it will not be an exact simulation of the specific light source.

Michael Vinther

> software developer <

mv's Website

3 Reply by Adam (edited by Adam 2014-03-18 22:38:21)

  • Adam
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Re: Spectral lines emulation

OK, thanks for your reply.

Setting the white balance can tone the image (actually, this is where I started) but it does not emphasize/suppress particular colours.

I've been thinking of something like taking the exactly same images of the printed colour spectrum under different light sources, analysing the changes in RGB values and applying them on the image in question.

I'm going to experiment a little and if I find an acceptable way, I'll describe it.

Btw. I don't believe that the reverse operation (i.e. restoring the image taken under a high pressure sodium lamp to look like taken under a full and continuous spectrum source) could be done.

4 Reply by Adam

  • Adam
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Re: Spectral lines emulation

The correct light source conversion can be done by using the ICC profiles for the sunlight and for the lamp with the line spectrum, details at http://photo.stackexchange.com/question … -emulation.

I guess the SLRs do it the similar way. For example, in my camera, there is a profile called "daylight fluorescent" and it seems to compensate the suppressed colours by that light source.

Note: IA does not seem to have features for ICC profile management, but I believe it uses them for the correct image displaying.
If the image associated ICC profile shouldn't be used, there is a checkable menu item Window - Use monitor colour profile .. (Correct me, if I'm wrong.)

5 Reply by mv

  • mv
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  • From: Denmark
  • Registered: 2003-09-17
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Re: Spectral lines emulation

If you include something white in the image you can make a selection on it and use the Adjust white balance feature to correct the image. That will do an adjustment similar to what the camera does.

Michael Vinther

> software developer <

mv's Website