Adobe Community: Disable Black Point Compensation

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1. Chris Cox,

Jul 4, 2012 1:52 PM in reply to piedpiedpiedpiper

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For image display, BPC will remain on (as it should be).

If RGB)0,0,0) shows up as something other than 0,0,0 - that means that BPC is off, and the profile has a problem.

BPC maps black to black, to correct problems with profiles that don't always map the darkest color correctly.

BPC off really only applies for print conversions (some of which you can simulate in proof settings).

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2. Jeff Schewe,

Jul 4, 2012 2:00 PM in reply to piedpiedpiedpiper

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piedpiedpiedpiper wrote:

In my understanding, we can turn off BPC with "Color Settings" daialog.

Unchecking the BPC in the Color Settings dialog turns off BPC for mode changes and color transforms...it doesn't have anything to do with how Photoshop displays your image and you can't control how Ps displays the image on screen other than soft proofing aside for the creation of the display profile and the display calibration. Not sure what "color picker application" you are referring to but if your display is showing 0, 0, 0 RGB as being lighter than max display black, something is wrong with the display calibration and profile.

Edit, plus what Crhsi says :~)

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3. piedpiedpiedpiper,

Jul 5, 2012 1:43 PM in reply to Jeff Schewe

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Thanks a lot!

Chris Cox wrote:
 
For image display, BPC will remain on (as it should be).

Jeff Schewe wrote:

Unchecking the BPC in the Color Settings dialog turns off BPC for mode changes and color transforms...it doesn't have anything to do with how Photoshop displays your image

I have investigated Photoshop's behavior in some environment, and the one indicates we may disable BPC for image display.

Ver.: CS6
OS: Mac OSX Lion
Monitor Profile: test_monitor_profile.icm (Created by Argyll CMS with i1 Display PRO)
Image File: 8color_adobe.tif (AdobeRGB profile embeded color chart.)
Color Picker Application: DigitalColor Meter (Lion has it as standard, and I believe it can capture device-RGB after the color conversion using monitor profile.)

On the above condition, the black patch RGB(0,0,0) shows device-RGB(5,3,2) in DigitalColor Meter In case of BPC ON in the Color Settings dialog.

And RGB(0,0,0) shows device-RGB(4,1,0) in case of BPC OFF. (Photoshop must be restarted to change the setting.)

These device-RGB values are the same as the ones in converted images by "Convert to Profile" dialog.

Therefore, I suppose the BPC check box in the Color Settings certainly affects the image display at least on the above condition, even if my monitor profile is wrong.

But the results in the other condition and your advice don't say so. I'm in confusion...

Please give me additonal suggestions and correct me if I am wrong.

Thanks in advance.

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4. Chris Cox,

Jul 5, 2012 3:45 PM in reply to piedpiedpiedpiper

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That monitor profile does have several problems (Version 2 profile whose whitepoint isn't D50, black input does not give black output, tables don't appear to be inverses, etc.).

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5. Gernot Hoffmann,

Jul 6, 2012 5:11 AM in reply to Chris Cox

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This monitor profile cannot be interpreted by Gretag-Macbeth Profilemaker.

Profile connection space is Lab. Normally one would use XYZ.

IMO there is no BPC for conversions between RGB working spaces and

monitor profiles. Working space black R=G=B=0 is mapped to monitor

values R=G=B=0 and appears with the darkest available monitor luminance.

Further discussions are here, including Adobe's BPC and Argyll comments:

http://www.google.de/search?hl=de&as_q=&as_epq=Adobe+BPC&as_oq=&as_eq= &as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=im ages&as_filetype=&as_rights=

Best regards --Gernot Hoffmann

Correction

Sorry, my mistake! I didn't check the box in front of the profile name

(which is normally not necessary, starting with one profile).

This gamut volume in Lab looks now quite normal.

Especially it reaches down to L*=0

Message was edited by: Gernot Hoffmann

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6. Chris Cox,

Jul 6, 2012 12:21 PM in reply to Gernot Hoffmann

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It's a table based profile, so LAB is just fine.

Also, check both tables for the profile - it doesn't always map to zero.

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7. piedpiedpiedpiper,

Jul 26, 2012 12:31 PM in reply to Chris Cox

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Sorry for not writing so long.

Chris Cox wrote:

Also, check both tables for the profile - it doesn't always map to zero.

I have studied ICC standard and Adobe BPC document during the blank period:), but I couldn't understand the profile which doesn't map to zero is illegal.

In fact, many printer profiles don't map to zero.

So the Photoshop's behavior in my post #3 is still mystery.

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Photoshop General Discussion

Disable Black Point Compensation

Jul 4, 2012 1:15 PM

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