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Author Topic: Soft proof bug in Photoshop CC?  (Read 1649 times)

digitaldog

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Soft proof bug in Photoshop CC?
« on: April 29, 2015, 10:46:52 am »

Wondering if anyone can confirm or deny what appears to be a bug in soft proofing with Photoshop CC. It has to do with the preview not the numbers. If I open a document in Adobe RGB (1998) and soft proof it in that color space, I see the preview update! I don't see that in CS6. Again, if the source color space and the soft proof color space match, we should see no visual difference nor the numbers change. I'm running this on a Mac (10.10.3). Have screen captures if that helps.

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Redcrown

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Re: Soft proof bug in Photoshop CC?
« Reply #1 on: April 29, 2015, 12:25:29 pm »

Andrew,

From 2 years ago:  http://forum.luminous-landscape.com/index.php?topic=77619.msg621858#msg621858

Still happens on my Win7 CC2014 system (and completely different hardware than I had 2 years ago).

For me, it's a GPU issue. If I turn off GPU processing, the "issue" goes away.

Remember that you have to re-launch to get the GPU change to take effect.
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digitaldog

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Re: Soft proof bug in Photoshop CC?
« Reply #2 on: April 29, 2015, 12:31:57 pm »

Thanks, I can confirm that indeed, it's GPU on this end too.
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Tim Lookingbill

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Re: Soft proof bug in Photoshop CC?
« Reply #3 on: April 29, 2015, 01:58:46 pm »

I think this makes about the fifth GPU processing related preview bug I've come across since I started hearing the words OpenGL or GPU acceleration with image editing apps.

What is so useful about GPU processing if it's causing issues with photographers? Is the fault of the video card manufacturer or OS? We never needed any kind of acceleration with still images even going back to Photoshop 4. At least I never needed it even back then scanning prints and negatives.
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D Fosse

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Re: Soft proof bug in Photoshop CC?
« Reply #4 on: April 29, 2015, 03:04:47 pm »

This one is nothing. There's a really bad one that's been around several years, to this day unacknowledged by Adobe, even after several long discussions in the Adobe PS forum.

Typically, this bug shows up in ProPhoto files, as distinct cyan banding in the shadows, when you have GPU set to "Normal" or "Advanced" modes. In these modes, the display color management logic is performed in the GPU. When you turn it off or set it to "Basic", these color transforms are shifted back to the CPU - and the banding disappears.

And the really interesting part is that even sRGB as display profile exhibits this banding. So there's no doubt it's a real bug, and not faulty calibration or bad profiles.

But it doesn't stop there - even Adobe RGB and sRGB files are affected, although not as severely. There's no banding here, but black levels tend to get clipped a couple of values. This seems to affect LUT display profiles more than matrix.

But in all cases, relieving the GPU of color management and shifting it back to the CPU removes the problem altogether. Poof - gone.

And for all this - has anyone ever seen any speed improvements in Photoshop? Not me. So I've kept it at the "Basic" setting ever since. But I could probably just turn it off altogether and be just as happy.
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digitaldog

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Re: Soft proof bug in Photoshop CC?
« Reply #5 on: April 29, 2015, 03:25:50 pm »

And for all this - has anyone ever seen any speed improvements in Photoshop? Not me. So I've kept it at the "Basic" setting ever since. But I could probably just turn it off altogether and be just as happy.
Well when I tested CS6, I didn't see the effect then discovered I had GPU set to Basic which at least with this bug, doesn't show. So no, I didn't even know I wasn't using the 'highest setting'. I
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Tim Lookingbill

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Re: Soft proof bug in Photoshop CC?
« Reply #6 on: April 29, 2015, 03:36:30 pm »

And for all this - has anyone ever seen any speed improvements in Photoshop? Not me. So I've kept it at the "Basic" setting ever since. But I could probably just turn it off altogether and be just as happy.

I've read in the past on these GPU issues that some of Adobe's new Photoshop features utilizes it so it might put a damper on sales if it keeps folks from taking advantage of the new features.

Wonder if Adobe provides a list before the purchase that states which features require GPU acceleration. I'm sure there is buried somewhere on their site.

Or maybe you could just turn it on/off when the feature is used but then again it might conflict when it's combined in a layer stack for further editing. Not sure, it seems everything has to get way too complicated the more stuff has to be put in newer software for it to sell.
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D Fosse

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Re: Soft proof bug in Photoshop CC?
« Reply #7 on: April 29, 2015, 04:06:30 pm »

Well when I tested CS6, I didn't see the effect then discovered I had GPU set to Basic which at least with this bug, doesn't show. So no, I didn't even know I wasn't using the 'highest setting'. I

Not all systems are equally affected by this. I've tested with several monitor/calibrator/profile spec combinations, and it goes from barely noticeable (very slight banding, but no color banding) to really bad (obvious cyan/red banding). It's hard to see any pattern, except LUT seems worse than matrix.

But if you look for it, you'll see it. It was first demonstrated with examples by Noel Carboni in the Adobe Photoshop forum around CS5/CS6, and the interesting thing was that mr. Carboni was somewhat notorious for refusing to ever let his monitors see the business side of a calibration sensor. He was strictly sRGB all the way. But of course that ruled out any doubt that the bug was real.

Several Adobe engineers regularly contribute to this forum, like Chris Cox. IIRC he said at the time they'd look into it. But since then it's been quiet, so maybe they're still looking.
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