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12-22-2009, 10:39 PM   #1
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Blue Sky Banding

Hey guys. I've just done a bunch of photos from Joshua Tree california, and the skies were deep cobalt and gorgeous, but now when I export them to lo-res jpgs, there is some pretty posterization in the sky. It's not in the full size files, only when I crunch it down for web sizes. I'l post some tomorrow if I think about it. Are there way to fix this in editing, or by exporting a different way. Photos were exported from LR2 with 100% jpeg quality. Thanks!

12-22-2009, 11:29 PM   #2
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It might not be banding in the file but rather on your monitor. Keep in mind 99% of computers have cheap LCD's now so its not going to be something you can control.

It might be LR2 doing it also.

Jpg's with 100% quality usually wont band from my experience.

Can you show us the image here? I can look at it with a CRT and half decent lcd and let you know.
12-22-2009, 11:54 PM   #3
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Yup - happens all the time with perfect skies and Pentax. I go to J-Tree about once a year and I often have the same problem. The Sonora and Mohave deserts have such crisp, clear air, the blues are almost too pure.

Compound that with the fact that Pentax usually has the most color deviation in sky-blue (based on a Gretag MacBeth ColorChecker). Depending on the "calibration" (misnomer) profile you use, this gets even worse because the software tries to adjust for the false blues - causing more tonal and hue seperation.

If you are shooting raw, you have some play, but with really perfect skies, there is usually just not enough variation of hue to decrease the banding.

I suggest you try interjecting small amounts of stochastic noise. This can occasionally break up the banding.

Also - if you are changing the tone of the sky with curves, or contrast adjustments, you need to be careful. Overall shifts in tone usually are fine. It's when you go for the seperation - ie increase the contrast, that banding becomes more prominent. Sometimes, I'll correct tone for the whole image and then revert the sky and finally shift the tone. That way the contrast of the sky always remains the same.

Finally - changing color space can make a huge difference in banding. If it's a real issue, I suggest that you proof to SRGB, using whichever intent. Then convert to SRGB before converting for web (gives the most control).

Really, finally (haha), if you edit in high-bit, you should downsample to 8 bit before converting.

Good luck!

Frank.

PS. If you post a link to high-res copies and their corresponding low-res web images, I can take a look and see if I can suggest an alternate workflow.
12-24-2009, 12:59 AM   #4
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You're right, Frank. The skies in J-tree are too perfect. They're so crystal blue. I made the mistake of having a polarizing filter on, which only complicated the matter. I wasn't so much after that polarizing effect as I was after the stop and a half of light loss, since it was approaching high noon, and I was shooting with 3 flashes, and locked at sync speed, and I wanted to shoot at f/2.8. I can't post the images on here, since they're for a client. I'll PM both of you with hi-res and lo-res of one of the banded images. Thanks for the help!

12-24-2009, 01:14 AM   #5
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What happens when you output a TIFF instead of a JPEG?
12-24-2009, 01:15 AM   #6
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looking at the jpg now and there is some banding, its not better or worse on the resized image though.

i cant show you what i see on my monitor, but its pretty slight imo

more noticeable to me is the major amount of CA on the foot and the rocks.

Last edited by WerTicus; 12-24-2009 at 01:29 AM.
12-30-2009, 10:06 PM   #7
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Same problem

I'm having more or less the same problem using a circular polarizer filter. I've attached a couple of photos with the problem... The photo with the boat has obvious banding in the skies, and the one with the yellow house has something similar going on below the clouds on the right side of the photo. Both were shot as JPGS.

I'm trying to find out how to prevent this, and possibly how to fix it in the photo. The problem gets worse as I darken skies in editing software. Any tips would be appreciated!

Thanks,

Matt
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12-31-2009, 10:00 AM   #8
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QuoteOriginally posted by matt4661628 Quote
I'm having more or less the same problem using a circular polarizer filter. I've attached a couple of photos with the problem... The photo with the boat has obvious banding in the skies, and the one with the yellow house has something similar going on below the clouds on the right side of the photo. Both were shot as JPGS.

I'm trying to find out how to prevent this, and possibly how to fix it in the photo. The problem gets worse as I darken skies in editing software. Any tips would be appreciated!

Thanks,

Matt
I think you've pretty much screwed yourself. You have a combination of quantization error caused by not having enough bit depth and way too much contrast and saturation.
The jpeg artifacts from over compressing the files isn't helping matters either.

12-31-2009, 02:05 PM   #9
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Wheatfield is correct...

This is not a camera issue per se. It is a digital photography issue. There are limits to what can be done with JPEG within the constraints of bit depth (8 bits/channel), color space (probably sRGB on export), and available resolution (small proportions for e-mail). With JPEG, you only have 256 shades of blue. When the sky is intense, uniform, and strongly peaked at a particular wavelength, you are going to see banding.

Steve
12-31-2009, 04:54 PM   #10
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Color Space Change?

Thanks for the input. I normally shoot RAW, but I was in Brazil for a month and a half during that shoot and at roughly 100 photos per day, I had limited flashcard space. The original jpg was 2256x1504 though. I thought it might be a monitor issue, but the same artifacts appeared on the printed photos.

Would it help to change the color space from sRGB to something else in the camera?
12-31-2009, 05:14 PM   #11
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QuoteOriginally posted by matt4661628 Quote
Thanks for the input. I normally shoot RAW, but I was in Brazil for a month and a half during that shoot and at roughly 100 photos per day, I had limited flashcard space. The original jpg was 2256x1504 though. I thought it might be a monitor issue, but the same artifacts appeared on the printed photos.

Would it help to change the color space from sRGB to something else in the camera?
Changing to Adobe RGB might help a little bit in a very small % of situations, but the underlying problem isn't colour space, it's bit depth. The problem is jpegs, not colour space.
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