Participating Frequently

P: Rendering problem with saturated colors using Graphics Processor

Forum|Forum|10 years ago
April 21, 2015
20 replies
2039 views

Possible issue with use of graphics processor: rendering in Develop Module of wide-gamut colours in error, LR6, problem goes away when "Use Graphics Processor" unchecked, problem didn't occur in LR5.x

Graphic card: NVidia GeForce GTX 550 Ti, latest drivers (350.12 but also occured with 340.52). Win 7 Home Premium, 64-bit, LR6, CC version.

Problem is this: with a wide-gamut monitor, in Develop Module, highly saturated blues are the wrong tone. They have to be VERY wide gamut: the problem occurs only with blues outside Adobe RGB gamut. These blues are rendered OK if "Use Graphics Processor" is unchecked. Obviously, in Library module this isn't a problem as colours are limited to Adobe RGB anyway.

Also, even in Develop Module, colours are OK on the 2nd Lightroom monitor window, wrong only on the main Lightroom monitor. If I move the main window to the other monitor, then it's that monitor that's now wrong. In other words: it doesn't depend on the monitor (one's HP, one's Eizo) nor on the calibrator s/w (one's calibrated with iProfiler, one with ColorNavigator, both creating v2 icc profiles). The false tone rendering appears only on the main LR window and only in develop module, and only when "use Graphics Processor" is checked.

Not a huge problem, but appears to me to be a bug.

PS - Test image supplied that shows the problem. The blue blob bottom left, which is RGB 0,0,255 in ProPhoto RGB renders OK without the graphics processor but not with it on. Perhaps the issue is because (0,0,255) in ProPhoto isn't a real colour? In which case, I wonder why software rendering displays a reasonable attempt, but the graphics processor software doesn't? Perhaps the graphics processor engine doesn't manage unreal colours quite as gracefully as the software rendering.

If the problem is confined to ProPhoto "colours" outside the range of real colours, clearly it's not really an issue.

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proligde

Participant

Hi there, I can confirm this issue and it does have quite a severe effect on my system. I do have a color management profiles installed on my system which seems to affect/produce this error. Running current LR6 on current Win 8.1.

When turning GPU-Support on (Standard GeForce GTX750) my Develop view (Image No. 2) changes massively compared to my Library View (Image No.2) When deactivating GPU-Support No.2 looks exactly like No.1.

It seems to me that the GPU driven Display on the develop mode does ignore the monitors(!) color profile while the library view obeys it. When I remove the color profile from my monitor there is no difference anymore)

Regards - Max

C

CSS_SimonAuthor

Participating Frequently

Thanks for the info. I'm glad to help identify a bug, even one that is unlikely to affect any real photographs!

MadManChan2000

Adobe Employee

Hi Simon,

I was able to get to the bottom of this. As you suspected, the issue was limited to out-of-gamut colors, in particular, colors that lie beyond the CIE L*a*b* gamut (such as the blue primary of ProPhoto, since it's an "imaginary" primary). In any case, I've implemented a fix for this, so that the GPU case will handle this more gracefully and should closely match the existing non-GPU case going forward. This fix/improvement should make it into the next Camera Raw and Lightroom releases.

Thanks again for your report. As you correctly noted, this should not be a problem in practice, but it's good to make the internal GPU-based color management scheme more robust.

Eric

MadManChan2000

Adobe Employee

Thanks Simon. I was able to reproduce this easily (e.g., blue primary discrepancy) using the profile for the CS240, but not the other one. Still investigating.

C

CSS_SimonAuthor

Participating Frequently

The version I am looking at in LR is a Tif that I created in Photoshop. I posted a jpeg as this system won't accept a tif. However, I haven't seen it in any real photo, and perhaps it affects only "unreal" ProPhoto RGB colours outside the gamut of real colours. Further information: I see it on both my monitors: an Eizo CS240, calibrated with Eizo ColorNavigator 6 and an i1 Display Pro and also on an HP LP2475w, also calibrated iwth an i1 Display pro, but with xrite iProfiler software. Both monitors are wide-gamut, rather wider than Adobe RGB.

To me it doesn't seem like a major bug unless you also find it affects the rendering of "real" colours.

I'll email you the profiles.

MadManChan2000

Adobe Employee

Thanks for clarifying Simon. I see what you mean about the blues. Although, to my eye, I am seeing a pronounced "rim" or "edge" around the green primary in the non-GPU case, compared to the GPU case. Are you seeing the same with the real image on your screen? Wasn't sure if this discrepancy is due to the JPEGs as posted in the forums, or whether this is actually happening on your system.

Would you mind sharing with me your color profiles for your two screens? (i.e., the one that you're currently using?) You can either post download links or just email me privately (madmanchan@gmail.com).

Thanks,
Eric

C

CSS_SimonAuthor

Participating Frequently

This is a fairly minor difference in rendering - not even sure it's a bug.

The image I posted earlier is fully saturated primaries and secondaries in ProPhoto RGB. On the main monitor in LR6 in develop module, see the two different renderings below:

The rendering especially round the edge appears better with "use graphics processor" unchecked. The rendering on a 2nd monitor (ie. type control-E) is the same as with graphics processor off. In Photoshop it also renders as with graphics processor off.

The colours on these screen captures may not be accurate, but you can see the rather sharp way it renders round the edges with graphics processor on.

I've not seen any problem except with super-saturated ProPhoto blues (i.e. "unreal" colours).

MadManChan2000

Adobe Employee

Simon, I took a look at this on Lr side as well, but actually could not reproduce this problem. I took your test image from above with the various additive and subtractive primaries, opened in Photoshop, assigned ProPhoto RGB to it, saved it as a TIFF (with profile embedded), and left it open in Ps for reference.

I then opened this TIFF file in Lr CC. I viewed the image in Develop. I toggled GPU acceleration on/off; no difference. I compared the results side by side with Photoshop; also no difference. To be sure, I used a screen-grab utility to compare the colors and check the numeric values.

For the blue primary example that you mentioned, what do you see in GPU mode in Develop? That is, qualitatively, how does this differ in appearance from the "reference" non-GPU implementation in Develop?

Thanks,
Eric

MadManChan2000

Adobe Employee

Still looking into this, Simon. So far, I have confirmed that this problem does not happen in Camera Raw 9.0 (which offers the same GPU acceleration features as in Lr CC). This is somewhat unexpected. I need to take a closer look at what's going on differently in Lr now.

MadManChan2000

Adobe Employee

Thanks Simon, we're looking into this.

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