PHOTOSHOP: Banding in the sky/gradients after saving as JPEG

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  • Updated 4 years ago
  • (Edited)
I never noticed this before in previous versions of PS. I'm using PS CC.

My routine for the image retouching is-was effective but simple.

I export the RAW file from LR as 16bit image with Prophoto profile. I retouch it and at the very end I use the conversion to 8bit/srgb. The logic behind this is that I work with genuine 16bit colors, high gamut profile and after I finish all retouches the image goes back to 8/srgb or adobe profile. I can see slight colour changes when changing profiles, that's normal. This worked flawlessly before.

However, today I was working on 18mpix image with the whitish sky where I applied mild colour gradient. Everything looked smooth in 16bit. I did the conversion to 8/srgb and saved to JPG maximum quality, baseline standard. It looked fine. Histogram was clean and smooth. I closed the image and opened it again. And oh my! The sky was full of gradient's half-circles with histogram having jagged lines in the highlights. It was even more severe if I wanted to make the sky darker.

I get it - the image in the white part didn't have any information in terms of noise. It was mostly pure gradient and a little bit of colour, I guess 8bit couldn't handle it. However, the thing that still worries me is that Photoshop didn't show those effects realtime, when I converted the file to 8bit/srgb, nor did the histogram - but when I reopened the image.

Did I miss something here?

I don't remember I encountered this "feature" before... it was mostly what-you-see-is-what-you-get, with all pros and cons. Why PS CC didn't show the banding before reopening?
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ivan.planinar

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Posted 4 years ago

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Chris Cox

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JPEG is a lossy format, and 8 bit/channel to start with -- so it is possible that it introduced some visible quantization, even at maximum quality.
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ivan.planinar

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How come that I never noticed this before (and I have done tens of thousands of images)? I do see colour shifts if I change the colour space/profile and there's even the change in the texture if I zoom at 200-300%. I'm aware of that and it's fine as long as it suits my needs.

However, this was way different and much worse.

My main problem here is not the banding or any other 8bit limitation, but the thing that I'm not aware of this, until I close and reopen the jpg file.
Photoshop CC is NOT showing 100% preview of how the saved JPEG will look.
The result that I see after I open the file and when I can preview the changes during the JPG save are different.
I compared the results and my image in preview looks like it was saved at 8-9 quality setting. Much lower than 12. At 11-12 the image doesn't show any noticeable banding in preview, but it's there after I save it.
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Chris Cox

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I don't know - Photoshop's JPEG code hasn't changed.
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ivan.planinar

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Meh... I've checked similar Images I retouched with CS6 and the sky was flawless. :-/ Should I file a bug/feature request report?
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Chris Cox

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This is a bug report - now we need the images and exact steps/settings to reproduce the problem.