Granger Chart Soft Proofing Anomalies?

[lightshiner]

I've been experimenting with the Granger Chart sRGB IEC 61966-2.1 and Adobe Lightroom's Soft Proofing feature. I'm seeing Gamut Warnings when specifying a sRGB soft proofing colour profile (the warning area is much reduced if I switch the colour profile to Adobe RGB),

Is it possible that the sRGB Granger Chart includes colours which are not actually part of the sRGB gamut?

[digitaldog]

The gamut warning isn't accurate, ignore it. Same should be true in Photoshop.

[lightshiner]

Thanks for letting me know that Lightroom gamut warnings may not be accurate.

Such inaccuracy could explain why soft proofing based on a specific printer profile (ICM provided by a professional printing service) indicates that approximately 1/3 of the colours in the (sRGB) Granger chart are outside of the printer's gamut.

[hugowolf]

Thanks for letting me know that Lightroom gamut warnings may not be accurate.

Such inaccuracy could explain why soft proofing based on a specific printer profile (ICM provided by a professional printing service) indicates that approximately 1/3 of the colours in the (sRGB) Granger chart are outside of the printer's gamut.

That an sRGB file soft proofed in sRGB should show out-of-gamut colors in Lr and Ps isn't good, but soft proofing is still useful.

That 1/3 of an sRGB image's colors would be out of a print machine's gamut is another matter. (What printer?). sRGB will have colors that are out of most printer's gamut, but the printer's gamut will also have large areas that are out of the sRGB gamut.

Brian A

[lightshiner]

Thanks Brian for your comments.

The printer profile is from a Fujitsu printer using Fujifilm professional paper. I used Lightroom to reduce saturation to the point that there were no remaining gamut warnings, however, the corrected Soft Proofing image was much less saturated than the actual prints (from two printers). While the prints were not identical. the match between them was much better than either print and the corrected Soft Proofing image.

I've attached a screenshot of the Destination Gamut Warnings using the aforementioned printer profile.

BTW, I posted a similar message on the Photoshop feedback site: http://feedback.photoshop.com/photoshop_family/topics/suspicious-results-using-lightroom-soft-proofing?rfm=1

David S

[bjanes]

The gamut warning isn't accurate, ignore it. Same should be true in Photoshop.

I constructed Grainger rainbows in sRGB and ProPhotoRGB and soft proofed in PhotoshopCC with the device to simulate set as sRGB. I then turned on the gamut warning after having set the out of gamut warning to bright red to simulate the warning in Lightroom. The soft proof of the sRGB image (shown on the right of the screen capture) showed no out of gamut colors, in contrast to the situation with soft proofing in LR. The soft proof of the ProPhotoRGB image showed extensive out of gamut colors (left in the screen capture). The conclusion is that the gamut warning is more accurate with Photoshop than LR.

The problem with both out of gamut warnings is that an only slightly out of gamut color is not differentiated from a wildly out of gamut color. A color that is out of gamut by one ΔE would not be significant, but one that is out of gamut by 10 ΔEs would be highly significant. A pseudocolor representation of the amount by which a color is out of gamut would make the out of gamut warning more useful. Such a representation can be constructed with ColorthinkPro or Gamutvision. An example of such a Gamutvision gamut plot is shown below in the second image. The scale to the right shows the key for the gamut warning where yellow represents a ΔE of 1 or 2 (insignificant) and purple a ΔE of 7-8 (significant).

Cheers,

Bill

[lightshiner]

Thanks Bill ... very interesting.

I'm using the most recent version of Lightroom (LR6 released April 21st, 2015) so one would hope that the Soft Proofing would be equivalent to that of the current version of Photoshop.

I like your suggestion for determining the degree to which a colour is out of gamut. One simple technique would be to add a matching threshold to LR's Soft Proofing (or perhaps just restrict warnings to "significant", "perceptible", or "exact match" ) which would limit the reporting of out of gamut warnings.

- David S

[Redcrown]

Try this to get around the "anomolies" in Adobe softproofing (in Photoshop)

1. Dupe your larger colorspace image, then CONVERT the dupe to the smaller colorspace (Prophoto to sRGB).
2. Copy the dupe, paste it back onto the original. The paste will convert the smaller back to larger.
3. Put the new layer in Difference mode.
4. Add a layer to desaturate.

What you get is a grayscale view of out-of-gamut areas and a representation of how far things are out of gamut. Also, that grayscale can be used as a mask for adjustments if desired.

Doing this with Bill Atkinson's 28 balls is more dramatic than with a Granger Rainbow.

[lightshiner]

Try this to get around the "anomalies" in Adobe softproofing (in Photoshop)

1. Dupe your larger colorspace image, then CONVERT the dupe to the smaller colorspace (Prophoto to sRGB).
2. Copy the dupe, paste it back onto the original. The paste will convert the smaller back to larger.
3. Put the new layer in Difference mode.
4. Add a layer to desaturate.

What you get is a grayscale view of out-of-gamut areas and a representation of how far things are out of gamut. Also, that grayscale can be used as a mask for adjustments if desired.

Doing this with Bill Atkinson's 28 balls is more dramatic than with a Granger Rainbow.

Thanks Redcrown for the suggestion. Unfortunately, I don't have access to Photoshop but it is generally possible to change the colour space in LR while exporting (original image has an embedded sRGB colour profile). I could import an exported Pro Photo version of the (original sRGB) image and finally re-export using sRGB.

BTW, I like the idea of using the out of gamut warning regions as a mask to help bring such regions back into the available gamut (although different colours may possibly require different adjustments).

- David S

[digitaldog]

1. Dupe your larger colorspace image, then CONVERT the dupe to the smaller colorspace (Prophoto to sRGB).

Why sRGB of all color spaces?

[Bart_van_der_Wolf]

Why sRGB of all color spaces?

Web publishing, on-line printing services, ....?

Cheers,
Bart

[digitaldog]

Web publishing, on-line printing services, ....?

So convert to sRGB and you're done. You are forced into a RelCol conversion, the colors are going to clip to sRGB as expected. Why the mask, editing the image with OOG overlay if you're going to clip to sRGB?

[Bart_van_der_Wolf]

So convert to sRGB and you're done.

Not really, and you know it Andrew.

There may be issues that can be addressed while in the larger gamut space. Perhaps a targeted desaturation, or a hue shift, or a luminance adjustment will reduce the amount of clipping (and thus loss of distinction or posterization). Therefore a direct comparison, also of thee magnitude of clipping, and the ability to create a graduated mask to isolate the problem areas, is very useful. I also use the method that 'Redcrown' described, I have it in a Photoshop Action.

Cheers,
Bart

[digitaldog]

Not really, and you know it Andrew.

For Web publishing, on-line printing services, ....? Really?

[Redcrown]

Jeeze, Andrew.. I respect your knowledge and bow to your experience. But I wish you would stay on your drugs. Or go back to grade school and re-learn how to count to 10 before you pop off.

[Lundberg02]

This is complicated by the conversion being relative

[bjanes]

Why sRGB of all color spaces?

Because the OP was soft proofing with sRGB as the target. Redcrown's method could be used with a printer profile as the target, in which case the perceptual rendering intent could be used. He specifically refers to the smaller color space, and sRGB was only an example of a smaller space. I haven't yet tried the method, but it appears interesting.

ColorthinkPro is perhaps the gold standard for these gamut comparisons, but try feeding it a 100 MB 16 bit file. One has to drastically downsize such a file and then generate a color list--a very time consuming process. Gamut vision can be used directly with large files, but it is Windows only and hasn't been updated for a while and will not even install on my Windows 8.1 desktop.

Bill

[digitaldog]

Redcrown's method could be used with a printer profile as the target, in which case the perceptual rendering intent could be used. He specifically refers to the smaller color space, and sRGB was only an example of a smaller space. I haven't yet tried the method, but it appears interesting.

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?

[lightshiner]

Thanks for all the comments...

At the risk of unleashing a firestorm, I chose the sRGB since both my camera and my intended printer support this colour space. As was mentioned, probably both devices may support a gamut that is actually wider than sRGB (e.g. the camera also supports Adobe RGB). I thought that using sRGB would help ensure that image colours would be faithfully reproduced (especially by using Soft Proofing with the colour profile provided by the printing service).

I view/edit images using Lightroom 6 on a 32" LED monitor (actually a Samsung 720p TV connected via HDMI) that has been calibrated using the Datacolor Spyder4 Express device/utility software. According to this utility, the monitor covers 98% of the sRGB gamut. So from my naive colour management perspective, it seems like sRGB is a good choice given that the camera, printer, and monitor all cover a large portion of the SRGB colour space.

BTW, I recall reading that Lightroom itself uses Adobe RGB internally (except for the develop module where Pro Photo is used).

- David S

[digitaldog]

BTW, I recall reading that Lightroom itself uses Adobe RGB internally (except for the develop module where Pro Photo is used).

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.