Vignetting, discussion about methods of resolution Options

[Tman]

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

[jrdahlman]

Is this anti-vignetting program specifically for MER photos? I had no idea.

You see, I have an old two-CD-ROM program called "Voyage to the Outer Planets" that includes "Voyager's Greatest Hits," a sample of original IMG files from the Grand Tour. They're the original 800 x 800 complete with reseau marks, and the vignetting is AWFUL. All the images get lighter, not darker, as you get near the edge. It makes homemade stitching look terrible. (Apparently you're supposed to correct them against something called "flatfield" images, but there's nothing like that on the CD. How do you do that?)


I tried the old version on a borrowed XP machine with some Jupiter pictures. It seemed to work OK, except for the extreme corners. Would I really need a corrected version for Voyager images? Or should all the images be temporarily made into negatives, so the edges do go darker instead of lighter?

Thanks.

[MichaelT]

Is this anti-vignetting program specifically for MER photos? I had no idea.
[...]
I tried the old version on a borrowed XP machine with some Jupiter pictures. It seemed to work OK, except for the extreme corners. Would I really need a corrected version for Voyager images? Or should all the images be temporarily made into negatives, so the edges do go darker instead of lighter?

Thanks.

Well, first I wrote the program specifically for MER images. So, the vignetting that the program is designed to remove is that of the MER cameras, which have vignetting very close to r^2. So you can use it for all images that have vignetting of that kind.
I know the "extreme corner problem", too, which I encountered with images that I had taken with a digital camera. It results from vignetting of higher orders I suppose. So, unfortunately, I suspect, the anti-vignetting program will not be able to eliminate it. Can you post one of the images here so that I can have a go?

Michael