Vignetting, discussion about methods of resolution |
Vignetting, discussion about methods of resolution |
Aug 24 2005, 07:37 AM
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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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Jul 5 2006, 04:47 PM
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Junior Member Group: Members Posts: 37 Joined: 20-November 05 Member No.: 561 |
Sorry for the delay. My website requires me to upload files one at a time.
(Warning: lots of links follow.) I was trying to hand-stitch two Voyager Jupiter images: C1631753 and C1631755. Here's what it looks like if you just use the uncorrected images: Ugly. Here are the two of them from my "Voyager's Greatest Hits" CD-ROM, in various versions: C1631753: the NASA "IMQ" file converted with IMG2PNG jpegged C1631755: the NASA "IMQ" file converted with IMG2PNG jpegged I fed the jpgs into your original anti-vignetting program, and it came up with this: C1631753_AV.jpg C1631755_AV.jpg Not understanding the controls, I also tried them with "pixel protect" set to 0%, whatever that does: c1631753_av0pct.jpg c1631755_av0pct.jpg If you want to see Voyager's vignetting on a blank image, the closest I have is C2683716. (It's actually a look at the moon 1985u1, so there's a dim disc near the middle you can ignore.) C2683716: the NASA "IMQ" file converted with IMG2PNG jpegged The program didn't know what to do with it: C2683716_AV.jpg Anyway, a mosiac is improved but not perfect: (Darn it, I can line up the moon or the clouds but not both. Voyager couldn't have moved that fast in 2 minutes! Maybe one needs to be tilted. voy755753clouds.jpg Wish I had an auto-stitch program that would run on my machines.) |
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Jul 6 2006, 01:01 PM
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Senior Member Group: Members Posts: 3652 Joined: 1-October 05 From: Croatia Member No.: 523 |
(Darn it, I can line up the moon or the clouds but not both. Voyager couldn't have moved that fast in 2 minutes! Maybe one needs to be tilted. Oh, yes, it could have moved that fast! In fact, it's probably not Voyager's perspective that changed that much as much as Europa progressed onward in its orbit + the clouds themselves are racing too, remember Jupiter is the fastest rotating planet. Europa orbits at a few kilometers per second and that's more than enough to change its position drastically in 2 minutes. -------------------- |
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