Granger Chart Soft Proofing Anomalies?

[bjanes]

Pointless, we have soft proofing, we can and should edit via soft proofing.
The conversion made for brining the OOG comparison was made using, oh my, a profile! We can use it for soft proofing (since 1998) and for affecting OOG colors for the conversion, exactly what the technique does before all the futzing around manually. Doing this for sRGB to pop onto the web? Seriously?

Editing via soft proofing is fine, but problems can arise when one is editing colors that are out of the gamut of the monitor. Shown below is the gamut of my monitor (calibrated with Spectraview and the NEC colorimeter) and the gamut of my printer with Epson Premium Glossy paper as described by the Epson profile. Some yellows and teal-greens are out of the gamut of the monitor but within that of the printer. The monitor is advertised as wide gamut. I've read your previous posts where you advise that if one is editing the colors of the file and the changes are not shown on the monitor, the gamut of the monitor may have been exceeded.

Lightroom does try to help in this situation by also giving a gamut warning for the monitor. What do you think of that?

Regards,

Bill

[digitaldog]

Lightroom does try to help in this situation by also giving a gamut warning for the monitor. What do you think of that?

I think it's useful and could be far more useful.

[lightshiner]

Internally it uses ProPhoto RGB primaries with a linear TRC. For previews outside Develop, it's Adobe RGB (1998) unless something has changed. But the processing is done with ProPhoto RGB gamut.

Andrew,

Thank you for clarifying. Actually, this makes perfect sense since I understand that Pro Photo is the widest gamut (compared to sRGB and Adobe RGB). BTW, I had to look up TRC (Tone Response Curve).

I'd be curious to know if the wide gamut of the 4k Ultra HD specification will necessitate a revision to Pro Photo as the gold standard for photography.

Regarding my original query, I've sent a note to Adobe asking if someone could have a look at this apparent anomaly.

- David S

[lightshiner]

...

Lightroom does try to help in this situation by also giving a gamut warning for the monitor. What do you think of that?

Bill,

I've also noticed some unexpected behaviour with LR's Monitor Gamut Warning. I'd be curious to know if you're observing the same with your (advanced) setup.

Steps:

• select image (e.g. Granger chart). turn on Soft Proofing with Monitor and Destination Gamut Warnings both enabled
  
• select the monitor's colour profile as the Destination profile (use Other with Include Display Profiles checked)
  

Now since the same colour profile is used for both gamut warnings, colours outside of both gamuts should be highlighted in pink (i.e. red for destination, blue for monitor). However, the image below shows only Destination Gamut Warnings.

- David S

[bjanes]

Bill,

I've also noticed some unexpected behaviour with LR's Monitor Gamut Warning. I'd be curious to know if you're observing the same with your (advanced) setup.

Steps:

• select image (e.g. Granger chart). turn on Soft Proofing with Monitor and Destination Gamut Warnings both enabled
  
• select the monitor's colour profile as the Destination profile (use Other with Include Display Profiles checked)
  

Now since the same colour profile is used for both gamut warnings, colours outside of both gamuts should be highlighted in pink (i.e. red for destination, blue for monitor). However, the image below shows only Destination Gamut Warnings.

- David S

David,

I performed your suggested test with my setup (which is no more advanced than yours, I suspect).

With the Grainger in sRGB and soft proofing with the monitor profile as the destination, no out of gamut is observed for the monitor, but the destination shows some out of gamut colors. Since my monitor is wide gamut (approximately AdobeRGB), there should be no out of gamut at all.

With the Grainger in ProPhotoRGB and soft proofing with the monitor profile as the destination, severe out of gamut is present in the destination, but the monitor shows no out of gamut, which is impossible.

I did check to make sure that the system was using the proper profile for my display, and it was as shown in the third image below. I conclude that the monitor gamut warning is seriously defective.

Cheers,

Bill

[lightshiner]

David,

I performed your suggested test with my setup (which is no more advanced than yours, I suspect).

With the Grainger in sRGB and soft proofing with the monitor profile as the destination, no out of gamut is observed for the monitor, but the destination shows some out of gamut colors. Since my monitor is wide gamut (approximately AdobeRGB), there should be no out of gamut at all.

With the Grainger in ProPhotoRGB and soft proofing with the monitor profile as the destination, severe out of gamut is present in the destination, but the monitor shows no out of gamut, which is impossible.

I did check to make sure that the system was using the proper profile for my display, and it was as shown in the third image below. I conclude that the monitor gamut warning is seriously defective.

Cheers,

Bill

Thanks Bill for confirming that a single colour profile produces vastly different results when specified as a Destination Profile or when specified as a Monitor Profile. For the time being, I think it's safer to ignore the gamut warnings than to modify (e.g. desaturate) the image based on these warnings.

Apart for Soft Proofing gamut warnings, has it been your experience that the Soft Proofing preview gives a reasonable rendition of the eventual print? If I compare the attached image to the corresponding print of the Granger Chart, Soft Proofing seems very approximate. Of course, this could reflect an inaccurate profile as opposed to a deficiency in Soft Proofing.


Regards,

David

[digitaldog]

For the time being, I think it's safer to ignore the gamut warnings than to modify (e.g. desaturate) the image based on these warnings.

Amen to that brother! Huge waste of time, spend it more productively elsewhere.

[lightshiner]

Thanks Bill for confirming that a single colour profile produces vastly different results when specified as a Destination Profile or when specified as a Monitor Profile. For the time being, I think it's safer to ignore the gamut warnings than to modify (e.g. desaturate) the image based on these warnings.

...

Regards,

David

An explanation of the Monitor Gamut Warnings behaviour ...

From Suspicious Results using Lightroom?

LRuserXY
The monitor gamut warning is implemented _after_ the conversion to the target color space, so if both are equal, there will be no monitor warning regarless of the original saturations.

This was changed in some early beta (?) stage when the softproof was introduced, and I think there was an explanation by Eric Chan why this was changed in the Adobe forums. Unfortunetely, this was never explained in Adobes official Lightroom help/documentation.

Original forum thread (Jao vdLs post and Eric Chans answer "The current behavior is a bug and will be fixed").

It seems logical, because if I want to softproof using a printer profile, I am not interested in the areas that exceed the monitor gamut in the _original_ image. I am only interested in the areas that exceed the monitor gamut in the _converted_ image - because only these areas will _not_ look the same on the monitor vs. printed output.

[bjanes]

An explanation of the Monitor Gamut Warnings behaviour ...

From Suspicious Results using Lightroom?

LRuserXY
The monitor gamut warning is implemented _after_ the conversion to the target color space, so if both are equal, there will be no monitor warning regarless of the original saturations.

This was changed in some early beta (?) stage when the softproof was introduced, and I think there was an explanation by Eric Chan why this was changed in the Adobe forums. Unfortunetely, this was never explained in Adobes official Lightroom help/documentation.

Original forum thread (Jao vdLs post and Eric Chans answer "The current behavior is a bug and will be fixed").

It seems logical, because if I want to softproof using a printer profile, I am not interested in the areas that exceed the monitor gamut in the _original_ image. I am only interested in the areas that exceed the monitor gamut in the _converted_ image - because only these areas will _not_ look the same on the monitor vs. printed output.

I had not looked at the issue that way, but the observed behavior does make the most sense and I must retract my statement that the monitor gamut warning is seriously flawed. Eric Chan understands the issues better than I, and the monitor gamut warning could be useful.

Bill

[lightshiner]

I have a hypothesis to explain my original observations but need the group's expertise as to whether this explanation is, in fact, plausible.

Let's assume that the sRGB Granger chart has been properly generated and that its embedded sRGB profile correctly matches the colour space used to generate the image. Also recall that there is no control for the sensitivity of Soft Proofing gamut warnings. I assume then that even minor (perhaps barely perceptible) colour mismatches will be flagged with Destination gamut warnings.

I understand Lightroom performs all its internal calculations using the (very wide gamut) Pro Photo colour space. Thus both the specified soft proofing sRGB profile and the embedded image sRGB profile would have to be converted to Pro Photo.

I suspect that small differences in the sRGB profiles (or possibly LR is using a slightly different conversion algorithm in each case) could account for the observed gamut warnings. To verify this explanation, one would have to be able to measure the deviation between the flagged image colours and the corresponding reference colours used by Soft Proofing.

Comments?

- David

[lightshiner]

I have a hypothesis to explain my original observations but need the group's expertise as to whether this explanation is, in fact, plausible.

Let's assume that the sRGB Granger chart has been properly generated and that its embedded sRGB profile correctly matches the colour space used to generate the image. Also recall that there is no control for the sensitivity of Soft Proofing gamut warnings. I assume then that even minor (perhaps barely perceptible) colour mismatches will be flagged with Destination gamut warnings.

I understand Lightroom performs all its internal calculations using the (very wide gamut) Pro Photo colour space. Thus both the specified soft proofing sRGB profile and the embedded image sRGB profile would have to be converted to Pro Photo.

I suspect that small differences in the sRGB profiles (or possibly LR is using a slightly different conversion algorithm in each case) could account for the observed gamut warnings. To verify this explanation, one would have to be able to measure the deviation between the flagged image colours and the corresponding reference colours used by Soft Proofing.

Comments?

- David

I've used the ExifTool to extract the following information directly from Granger Chart sRGB IEC 61966-2.1.jpg (Copyright 2011© Douglas Janson) and from an image exported from Lightroom.

Granger sRGB Profile
Device Manufacturer             : IEC
Device Model                    : sRGB
Device Attributes               : Reflective, Glossy, Positive, Color
Rendering Intent                : Media-Relative Colorimetric
Connection Space Illuminant     : 0.9642 1 0.82491
Profile Creator                 : HP
Profile ID                      : 0
Profile Copyright               : Copyright (c) 1998 Hewlett-Packard Company
Profile Description             : sRGB IEC61966-2.1
Media White Point               : 0.95045 1 1.08905
Media Black Point               : 0 0 0
Red Matrix Column               : 0.43607 0.22249 0.01392
Green Matrix Column             : 0.38515 0.71687 0.09708
Blue Matrix Column              : 0.14307 0.06061 0.7141
Device Mfg Desc                 : IEC http://www.iec.ch
Device Model Desc               : IEC 61966-2.1 Default RGB colour space - sRGB

Lightroom sRGB Profile
Device Manufacturer             : IEC
Device Model                    : sRGB
Device Attributes               : Reflective, Glossy, Positive, Color
Rendering Intent                : Perceptual
Connection Space Illuminant     : 0.9642 1 0.82491
Profile Creator                 : HP
Profile ID                      : 0
Profile Copyright               : Copyright (c) 1998 Hewlett-Packard Company
Profile Description             : sRGB IEC61966-2.1
Media White Point               : 0.95045 1 1.08905
Media Black Point               : 0 0 0
Red Matrix Column               : 0.43607 0.22249 0.01392
Green Matrix Column             : 0.38515 0.71687 0.09708
Blue Matrix Column              : 0.14307 0.06061 0.7141
Device Mfg Desc                 : IEC http://www.iec.ch
Device Model Desc               : IEC 61966-2.1 Default RGB colour space - sRGB

Update 1: I tried to remove the Destination Gamut Warnings by using the Primary Saturation sliders. Contrary to my hypothesis, the gamut warnings are highlighting colours that Lightroom believes are well outside the gamut that Soft Proofing is testing for (see attached screenshot).

Update 2: Photoshop Feedback user LRuserXY noted that turning the GPU on or off affects the gamut warnings displayed. I confirmed this for the Granger chart. The Destination Gamut Warning area is larger when the GPU is enabled. This behaviour may be confirmation that colour characterization is a highly sensitive to calculation errors.

Update 3: When I extracted LR's sRGB profile from an JPEG exported RAW file and viewed the Exif data, I noticed a difference in the Rendering Intent (see above).
Q: Could this difference possibly impact the display gamut warnings?
A: No, gamut warnings are independent of the Rendering Intent.

See Introduction to Rending Intents and Understanding Rendering Intents for more information.

Update 4: Using an ICC profile viewer, the SRGB and embedded Granger Chart gamuts seem to be identical (see attached plot).

Update 5: Final nail in the coffin => sRGB Granger Chart soft proofed with its own (embedded) colour profile still displays identical gamut warnings (see Gamut Warning for Granger Chart Soft Proofed with own Colour Profile). I am convinced that observed behaviour is due to a deficiency within Lightroom.


- David

[Jim Kasson]

I'd be curious to know if the wide gamut of the 4k Ultra HD specification will necessitate a revision to Pro Photo as the gold standard for photography.

In a word, no.

The Rec 2020 gamut is contained within the PPRGB gamut.



Jim

[lightshiner]

In a word, no.

The Rec 2020 gamut is contained within the PPRGB gamut.

Jim

Thanks Jim ... That's reassuring.

- David

[lightshiner]

As mentioned, there are related LR6 issues with the GPU enabled. See Suspicious Results using Lightroom Soft Proofing and LightRoom 6: Inaccurate Develop Preview Colour Mapping for ColorChecker Chart for more details.

- David

[bjanes]

In a word, no.

The Rec 2020 gamut is contained within the PPRGB gamut.



Jim

Jim,

How does the gamut of Rec 2020 compare to AdobeRGB? I understand that it is somewhat wider; if so, are there monitors capable of displaying this gamut?

Bill

[Jim Kasson]

How does the gamut of Rec 2020 compare to AdobeRGB?

Here you go:

I understand that it is somewhat wider; if so, are there monitors capable of displaying this gamut?

I don't know.

Jim