Vignetting, discussion about methods of resolution |
Vignetting, discussion about methods of resolution |
Aug 24 2005, 07:37 AM
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#1
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Member Group: Members Posts: 877 Joined: 7-March 05 From: Switzerland Member No.: 186 |
Hi Nirgal and all, I would like to discuss about vignetting and methods of resolution for it. I'm mainly interested in mathematical methods that could automatically calculate and adjust the right grey value for each pixel in a single picture.
My current method works with more or less transparent layers over the original picture that so roughly are able to balance the grey values. A perfect layer have to be the exact inverted brightness difference of each picture with this shadow effects. This method is very effective if you get the correct inverted values. These shots of the Mars sky come nearly at such a perfect mask, but not always. And of course the center of the pictures lose much of theirs original brightness/luminance sadly. I have in mind a mathematical method that can adjust each grey value in a pic in order to obtain a completely balanced brightness over the entire picture. But I'm not in the position to reach that. I only know one have to start with the calculation of the grey values in the center of the picture. In the center are quasi the reference values of the whole picture, if I'm correct. Is there a possibility (mathematical method) to get (roughly) the same brightness and luminance like in the center over the whole picture from the MERs? Greetings, Peter -------------------- |
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Nov 14 2005, 11:15 PM
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#2
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Member Group: Admin Posts: 468 Joined: 11-February 04 From: USA Member No.: 21 |
Michael, thank you for sharing the code to this application. I've found the program very useful, and look forward to digging into its inner workings a bit deeper.
Jared, since vignetting is a camera effect, I'm pretty sure it would be inappropriate to use this application in Lab space. The L channel is shaped similar to a cube root function as it is intended to be a perceptive measure of brightness, and is therefore not linear with photon count like the raw images (well, in a perfect world at least . This means the 'fit' used to determine the amount of vignetting would be even more complicated if you used L instead of the actual pixel brightness through a given filter. The ab parameters concern themselves only with the ratio between color channels (or in MERs case, the raw images) and the only way to know if you have accurately described those would be to use this on the raw images before determining the color at each pixel. |
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