ArgyllCMS profiles: Black Point Compensation gives composite black when checked

[Ink stained Fingers]

Lightroom is broken then - either report the bug to Adobe, or use something else to print images.

The issue with Lightroom and 'BPC on' came up several years ago, there is a remark in this document further down

https://www.colourphil.co.uk/lightroom-cc-print.shtml

' Black Point Compensation: In Lightroom it can't be selected, as it's always 'ON', which is highly desirable. It will map the Black Point of the original image to that of the printer profile, helping to prevent dark shadows from filling-in.'

There was some confirming statement similar to this one in some Adobe document somewhere which about nobody is reading.
So this is quite contradicting to other Adobe comments not to use 'BPC on' - it's not a problem with Photoshop. I'm not using either one to print.

 

[Tony4597]

I have never come across Adobe recommendation for BPC off. Any chance of a link to the source not to use BPC?

In fact I have been given to understand that Adobe In most cases, doing RGB to RGB conversions with Black Point Compensation will produce desirable prints.
With the option checked PS looks at black points of both profiles to see if the black levels are going to give acceptable results from source to destination. If PS determines that the black points are different it adjusts to make sure that the source profile is correctly mapped to the destination profile.

BPC will either produce acceptable results or have no effect when using modern profiles. AFAIK BPC is automatically handled in Lightroom by its algorithms selecting the most appropriate setting

Adobe systems implementation of Black Point Compensation
https://www.color.org/adobebpc.pdf

 

[Ink stained Fingers]

This thread is closed for me, but a few last comments

AFAIK BPC is automatically handled in Lightroom by its algorithms selecting the most appropriate setting

The quoted Adobe BPC document above does not support this automatic mode

Sect. 6.2 states

6. 2. Rendering intent
Typically, BPC is performed for conversions using the Relative Colorimetric intent. BPC is not available for conver-
sions using Absolute Colorimetric intent.
Color conversion using Perceptual intent already maps source white to destination white and source black to desti-
nation black. Because this mapping preserves the relationships of the shades, it is unlikely that a whole shadow
section will be mapped to the same black value. Therefore, BPC should not be necessary. BPC is available, however,
for this rendering intent, to be used with malformed profiles. For a given picture, the user can decide whether using
BPC improves the color conversion and can select it or deselect it accordingly.
BPC is available for color conversion using the Saturation intent. As with Perceptual intent, the user may or may
not find that selecting BPC improves the conversion of a given image

It's the user who selects the BPC option - if he can. And this document does not elaborate any further about the 'malformed' profiles . Could it be one like this - done with Datacolor Spyderprint - look here in this posting

https://www.printerknowledge.com/th...r-print-profile-comparisons.13275/post-122562

Case closed

 

[Tony4597]

This thread is closed for me, but a few last comments

Why, I thought you were happy to discuss?

You did state in this thread:

Adobe's position is ambiguous - they recommend BPC off unlesss really needed, but the problem comes up with Lightroom which has BPC on all the time for the perc. intent .

I only asked where you had seen the Adobe statement recommending BPC off unless really needed, which I do not think an unfair ask. I am really not trying to pick an argument here, merely trying to establish facts!

About no Lightroom user is aware of that and gets misleading results with the softproof function.

Again I have never seen any indication of issues with LR regarding misleading results with the soft proofing function; unless using a whacked profile. I have produce thousands of prints via LR softproofing without issue with a good profile.

LR softproofing module allows you to select profile and rendering intent (only Perceptual or Relative) and choose to simulate paper and ink. It is in the Print module where you select the final rendering intent and indeed Adobe state that Black Point Compensation will be used for this print.

Finally quotes from a well known author and consultant in colour management Andrew Rodney on BPC

You can't turn off BPC in Lightroom (and there's no reason to do so).

BPC was designed to fix an issue with mapping source to destination black. When a profile isn't following spec. Otherwise it does nothing.

It is optional in PS. It isn't in LR which attempts to simplify color management and that's why Adobe keeps on always.

Now truth be told, not everyone is in agreement about this, or that BPC is even necessary. I've yet to see a reason to turn it off. The qualities of the profile and how it deals with source to destination black plays the big role here, so maybe someone who's worked with profiles built in other packages has a different experience.

The automatic settings reference to the fact that LR decides to do something if the profile is not following spec otherwise it does nothing as highlighted above in AR comments

 

[Ink stained Fingers]

I thought you were happy to discuss?

Yes, I am - but this thread got already quite complex and voluminous which is the prime reason for me to come to an end.

I checked several postings about a similar issue from 2 and 3 years ago and found that some links to Datacolor and other don't exist anymore and that some other documents got updated since then and do not reflect the original meaning anymore or got cleaned up with a newer version, Datacolor profiles should not be used at all with BPC on and only with the rel. col. rendering intent. And as Andrew Rodney confirms that Lightroom keeps BPC always on the combination of LR with Datacolor profiles just does not work well . I'm not using either one software so I'm not persuing this any further.

 

[Tony4597]

Yes, I am - but this thread got already quite complex and voluminous which is the prime reason for me to come to an end.

I checked several postings about a similar issue from 2 and 3 years ago and found that some links to Datacolor and other don't exist anymore and that some other documents got updated since then and do not reflect the original meaning anymore or got cleaned up with a newer version, Datacolor profiles should not be used at all with BPC on and only with the rel. col. rendering intent. And as Andrew Rodney confirms that Lightroom keeps BPC always on the combination of LR with Datacolor profiles just does not work well . I'm not using either one software so I'm not persuing this any further.

Reply appreciated thank you .

Ahh, Datacolor and profiles, now I see. Unfortunately this company comes into a lot of criticism at least from what I have seen in professional circles. Unstable, too much variation between samples etc. etc. TBH the only Datacolor product I have used years ago was the Spyder 2 for monitor calibration; I had no problems with it but others did and it was not up to the task of characterizing and profiling wide gamut monitors.

When it came to print profiling I really wished that the Datacolor spectrocolorimeter supplied with SpyderPrint would work well (I liked the price!), but once again it came into much criticism; enough for me to stay away and initially try the i1Studio which seems to be very good at the price point.

 

[pharmacist]

Ohh the Spyder Print 3: terrible device and never could get well performing profiles (the dreaded blue to purple shift for which I even had to tweak the target before printing to compensate for the purplish hue). The Colormunki Photo produces almost spot on profiles without tweaking and much much better compared to even the high quality profile with 729 patches with the Spyder Print 3 (which took a very long time to read).

 

[marco565]

I agree I returned the spyderprint I had very weird colours on the standard test images. if you are interested I could post a profile from spyderprint and ColorMunki with argycms

 

[darshan]

Interesting thread, I want to share my findings related to the black point of Argy profiles.

Some background - I've created a lot of profiles with a Calibrite CC Studio (same as the i1Studio, CM) with the manufacturer's profiling software and recently came across ArgyII CMS since the device is supported I gave it a go and compared the results.

The good - Argy profiles are more neutral compared to Calibrite, I love it for that!

The bad - Argy profiles have a lower Dmax compared to Calibrite, I've tried many different options but was not able to make any progress. In actual prints of a test image the blacks are less black and more shadow detail is lost so I installed Gamutvision to confirm, attached some screenshots

left side 1->2 is Calibrite and on the right 3->4 is Argy

1. The first set is relative with BPC on (it's how I typically print) - significantly lower Dmax with Argy
2. Second is relative with BPC off (I don't really print this way but I would if it helps) - still lower Dmax compared to Calibrite but a little higher than with BPC on
3. And finally perceptual with BPC off (I don't like perceptual with Argy, saturated colors gets washed out) - here Argy gives deeper blacks and yet another Dmax value. Calibrite Dmax stays constant at 1.97 regardless of intent and bpc setting

Do you guys think there is something here, or am I doing something wrong?

$ targen -v -d2 -G -g8 -f210 $ printtarg -v -iCM -h -R1 -T360 -p A4 $ chartread -v -H -T0.4 $ colprof -v -qh -S AdobeRGB1998.icc -cmt -dpp $ profcheck -v2 -k -s # max error = 0.63

 

[Graeme Gill]

The bad - Argyll profiles have a lower Dmax compared to Calibrite, I've tried many different options but was not able to make any progress. In actual prints of a test image the blacks are less black and more shadow detail is lost so I installed Gamutvision to confirm, attached some screenshots

I'm not seeing that from your plots. Colorimetric I can see that the Argyll black is slightly raised, but that is to be expected with an accurate colorimetric profile - the lowest L* black is not neutral, so you get minimum dE clipping, which has a worse L*. If the Calibrite profile is giving you a lower L* for colorimetric, then the profile is not giving you minimal delta E.

The Argyll Perceptual plot appears to be working as intended - a black that is progressive, and has an L* value darker than the Calibrite profile in either Colorimetric or Perceptual mode (D = 2.07).

Gamutvision's BPC seems to have problems though, making the black L* slightly worse.