Old 08-25-2013, 03:25 PM   #1
Oskar
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Default Help with compression

I have a doubt regarding edition: how do you avoid that effect on the lines such like this on the side of the cars? http://www.railpictures.net/viewphot...=448732&nseq=5

I think it has to do with JPG compression, though it looks like an oversharp issue.

Thank you very much.
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Old 08-25-2013, 04:25 PM   #2
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I've never had an eye for compression unless it was very bad, but what I am seeing is a blurry photo that was maybe over sharpened to try to overcome that.
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Old 08-25-2013, 04:47 PM   #3
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Quote:
Originally Posted by EMTRailfan View Post
I've never had an eye for compression unless it was very bad, but what I am seeing is a blurry photo that was maybe over sharpened to try to overcome that.
No, no; I left "sharpness" in the editor in 0, and I would have lower it more if it was possible. I can show you the original picture with some sharpening and there is no bluriness problem.
I'm not sure what's wrong.
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Old 08-26-2013, 01:02 AM   #4
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This is called "moire" and is caused by having a series of parallel lines a) very close to each other relative to the size of a pixel, and b) at a slight angle to the horizontal/vertical lines of the pixel alignment.

Fixes/improvements:
a) do not sharpen. If you need to sharpen, select all but the potential moire areas
b) try different resize formulas (bicubic, etc - whatever your software offers)
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Old 08-26-2013, 01:17 AM   #5
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Quote:
Originally Posted by JRMDC View Post
This is called "moire" and is caused by having a series of parallel lines a) very close to each other relative to the size of a pixel, and b) at a slight angle to the horizontal/vertical lines of the pixel alignment.

Fixes/improvements:
a) do not sharpen. If you need to sharpen, select all but the potential moire areas
b) try different resize formulas (bicubic, etc - whatever your software offers)
Thanks a lot.

I have noticed that it happens in those situations you mention, so it must be that. I have never heard of "moire" in this context, but I know what the concept means.

I didn't sharpen in this case, but the resize suggestion seems like a good idea to try.

Thanks again, I will see if I can improve this picture enough as to resubmit.

Last edited by Oskar; 09-03-2013 at 07:47 PM.
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Old 11-02-2013, 12:00 AM   #6
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Quote:
Originally Posted by JRMDC View Post
b) try different resize formulas (bicubic, etc - whatever your software offers)
I finally had some time to read and learn about "interpolation" and try different resize formulas. Well, you were right, I found a better way to do it.
I'm very grateful for your help. Better late than never.

Last edited by Oskar; 11-02-2013 at 12:11 AM.
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Old 11-02-2013, 01:07 PM   #7
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You are welcome!
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