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Author Topic: What about this Media White Point?  (Read 5874 times)
angelnavarrophotography
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« on: July 29, 2010, 10:41:54 PM »
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I recently purchased a new LaCie 526 for my Mac Pro 2.66 tower. It came with the renown BlueEye Pro software package and Colorimeter. After countless calibrations and hours spent with the LaCie techs there was no solution to the following problem. Here it is:

After allowing the 526 one hour of warm up I began calibrating. Set gamma to native 2.2. luminance to 95 cal/m2 and color temp to 6500K. After a lengthy calibration process, the calibration was complete and my monitor got a nice average delta of .4 with the gamma set to 2.2 and temp at 6500K and the luminance set to 95. Perfect right? Wrong! Although I followed the destructions to the letter there was still a problem. The monitor was calibrated correctly but my new ICC display profile contained a 'wtpt' tag - thats media white point tag - set to 5000K. As a result, Photoshop displayed an image tinged by this white point tag. A sweater from a known neutral image used for testing showed up orange. Softproofing revealed the same problem. I looked into the profile tags and discovered this offending tag. By the way, ColorSync does NOT read this tag, you must use software that can read all the tags of a profile.

So just for kicks, I downloaded a canned profile from LaCie's website specifically for my new display. I set it as the new system profile and visited Photoshop only to find the delightful surprise of a perfectly neutral image. Wow, that's magic? Wrong again! You see, the ICC profile downloaded from LaCie, though canned and generic, contained a correct media white point (6500K) and in turn was picked up by Photoshop who in turn got a correct reference point. However, even after calibrating 18 more times with settings ranging from here to there, the offending 'wtpt' tag was still there. There was no way around this problem and LaCie thought I was speaking "jiberish". Couldn't speak to a senior tech or anyone else who even had a remote idea of what I was talking about. Does anybody share this experience among those who have purchased a new LaCie 526 with its renown BlueEye Pro package. I now have it's next of kin the NEC 2690WUXi2 with the SpectraView II deal and the problem remains the same. I will go a few rounds with NEC and see what happens. I suspect it may be a ColorSync paradigm or a system issue with Snow Leopard. I am running 10.6.4 OSX Snow Leopard. Please feel free to chime in...
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digitaldog
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« Reply #1 on: July 30, 2010, 08:36:33 AM »
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I’d be less concerned with all the numbers and tags and ask, do you have proper screen to print matching? If so, move on. If not, you probably, like the rest of us, have to season to taste. That is, adjust WP and almost always luminance values to get a visual match.

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Andrew Rodney
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WillH
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« Reply #2 on: July 30, 2010, 04:49:20 PM »
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The "wtpt" (media white point) tag of a display profile should be D50 regardless of what the actual white point is. To quote from the ICC spec here:

http://color.org/ICC1v42_2006-05.pdf

Page 33:
"For displays, the values specified must be those of D50 normalized such that Y = 1,0 (i.e. 0,9642 1,0 0,8249)."

The actual white point of the display gets encoded into the "chad" chromatic adaptation matrix tag, and this is not something that you can easily reverse to see the value.

I believe there was a clarification on this issue by the ICC because early versions of the spec were open to interpretation that the actual white point of the display should be encoded into the "wtpt" tag.

If you want to find out what Photoshop is using for the white point of the display, you can always use the "Custom RGB..." trick. i.e.

1. In the Photoshop Color Settings dialog, *temporarily* select the "Monitor RGB - xxxxx" profile as your working RGB space.
2. Then select "Custom RGB..." in the list
3. The Custom RGB dialog should show the unadapted white point and chromaticities of the display.
4. Be sure to set your working RGB space back to whatever you were using previously.
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Will Hollingworth
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angelnavarrophotography
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« Reply #3 on: July 30, 2010, 11:37:50 PM »
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Great reply and interesting! Thanx. I will try your suggestion. However, I am forced into deeper waters of inquiry. It seems that this is a complicated workaround to a problem that could be better solved by having a 'wtpt' tag of 6500K. One test I did was to download LaCie's canned profile for my display, which contained a 6500K media white point, and upon installation the mysterious mismatch between Colorbyte's ImagePrint soft proof, as well as its actual output, and Photoshop's display of the image disappeared. In other words, everything appeared to match between Photoshop, ImagePrint and printed output perfectly. This led me, and others in the Tampa Bay area, to believe that the culprit was the media white point. To verify this I r-installed the custom ICC profile with its 5000K 'wtpt' and we were back to step one again. Frustrating!!! I either use a generic profile and live with imperfection in my editing or use a "custom created" ICC profile and deal with the yellow tinge. After paying out some much money I expected smoother results. Does all this make sense? Chime in again please...
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angelnavarrophotography
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« Reply #4 on: July 30, 2010, 11:47:51 PM »
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Hello,

I tried your suggestion. I opened a know neutral image and summoned the Color Setting in PS. Next, I selected Monitor - xxxxxxxxxxxxxxxxx, then selected Custom RGB which prompted another dialogue box presenting option under White Point. But I wasn't sure what was next. Did you say OK out of the box without changes and then return the Color Setting back to my previous settings (in my case Adobe RGB)? I saw no change take place. I also tried change White Point to D65 (6500K) and still saw no apparent change.
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angelnavarrophotography
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« Reply #5 on: July 30, 2010, 11:53:03 PM »
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Hi DigitalDog,

The numbers would not concern me if there was not a mismatch. Visual manipulation of display settings counters the purpose of buying one of these glorified screens. I am not an expert by any stretch, but I sense that there is something AJAR here that only a pro, like your self perhaps, can isolate for the rest of us. If I was able to download a generic ICC profile from LaCie which contained a 'wtpt' of 6500k, then that leads me to believe that an alternative must be possible to achieve in a version 2 ICC profile, therefore making soft proofing in PS CS4 effortless.

On a separate note, if in Photoshop I go under 'Edit' - 'Assign Profile' and assign my display ICC profile - I get a match! Why is this? Do I need to do this with all working files prior working on them?

Please respond with your comments.
« Last Edit: July 31, 2010, 12:12:18 AM by angelnavarrophotography » Logged
angelnavarrophotography
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« Reply #6 on: July 30, 2010, 11:58:58 PM »
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WillH,

I re-read and discovered I misread your suggestion. Your suggestion was to observe the information, not to fix the problem. Please accept my apologies. The dialogue box I am including as an attachment. When I dropped down to D65 it read x=.3127 and y=.3290 - not sure what that means but I thought you might. All I can say is that anything red on my display looks orangy/red due to "HuhHuh??"
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digitaldog
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« Reply #7 on: July 31, 2010, 11:37:13 AM »
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Quote from: angelnavarrophotography
Visual manipulation of display settings counters the purpose of buying one of these glorified screens.

Why’s that? The goal is a visual match between the two very different medias.

Quote
On a separate note, if in Photoshop I go under 'Edit' - 'Assign Profile' and assign my display ICC profile - I get a match! Why is this? Do I need to do this with all working files prior working on them?

Because you’ve basically turned off the Display Using Monitor Compensation from a working space to the display color space. You’d never assign this profile to that document.
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Andrew Rodney
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angelnavarrophotography
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« Reply #8 on: July 31, 2010, 01:17:45 PM »
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Quote from: digitaldog
Why’s that? The goal is a visual match between the two very different medias.



Because you’ve basically turned off the Display Using Monitor Compensation from a working space to the display color space. You’d never assign this profile to that document.

Please excuse any redundant questions, I am navigating foreign waters with all of this. Is d50(5000K) the only media white point option available? In other words, am I going to always find a media white point tag of 5000K regardless of what how calibration is performed? The only way I am getting screen to print matching is using the Generic LaCie profile which by the way contains a media white point of 6500K. I'm so confused... You are welcome to email me if the possibility exists that you and I may speak over the phone for a few minutes. I can respond with my tel number if you email me first at: angel@angelnavarrophotography.com
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digitaldog
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« Reply #9 on: July 31, 2010, 01:20:42 PM »
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Quote from: angelnavarrophotography
Please excuse any redundant questions, I am navigating foreign waters with all of this. Is d50(5000K) the only media white point option available? In other words, am I going to always find a media white point tag of 5000K regardless of what how calibration is performed? The only way I am getting screen to print matching is using the Generic LaCie profile which by the way contains a media white point of 6500K. I'm so confused... You are welcome to email me if the possibility exists that you and I may speak over the phone for a few minutes. I can respond with my tel number if you email me first at: angel@angelnavarrophotography.com

D50 and 5000K ain’t the same for one.

As Will said, there’s a spec within the ICC for the media white point. I really think this whole media white point is a red herring too. Alter the target calibration values (in either a standard illuminate or using a Kelvin value) to produce visual match to the print viewing conditions. Its totally doable. It does take some experimenting to get the right recipe. Again, the numbers are kind of meaningless (the only object that could produce something like D50, which is a number of measurements averaged is 93 million miles away).
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Andrew Rodney
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angelnavarrophotography
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« Reply #10 on: July 31, 2010, 01:44:31 PM »
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Quote from: digitaldog
D50 and 5000K ain’t the same for one.

As Will said, there’s a spec within the ICC for the media white point. I really think this whole media white point is a red herring too. Alter the target calibration values (in either a standard illuminate or using a Kelvin value) to produce visual match to the print viewing conditions. Its totally doable. It does take some experimenting to get the right recipe. Again, the numbers are kind of meaningless (the only object that could produce something like D50, which is a number of measurements averaged is 93 million miles away).

Thank you for the prompt reply. You say its doable and that's encouraging. Can you give some direction? Howzitdone... How do I coerce the calibration process to to yield me my red herring (5000K media white point? Or am I still splitting hairs?
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digitaldog
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« Reply #11 on: July 31, 2010, 01:52:34 PM »
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Quote from: angelnavarrophotography
Thank you for the prompt reply. You say its doable and that's encouraging. Can you give some direction? Howzitdone... How do I coerce the calibration process to to yield me my red herring (5000K media white point? Or am I still splitting hairs?

In terms of white point, you build one at say D50 and view the soft proof, adjust up or down based on what you see. Too warm, go a higher value (D55). Same with the luminance. Adjust Cd/m2 for a match. I’d nail that first, then play with the white point which may not need any adjustment once that’s nailed.
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Andrew Rodney
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angelnavarrophotography
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« Reply #12 on: July 31, 2010, 01:58:09 PM »
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Quote from: digitaldog
In terms of white point, you build one at say D50 and view the soft proof, adjust up or down based on what you see. Too warm, go a higher value (D55). Same with the luminance. Adjust Cd/m2 for a match. I’d nail that first, then play with the white point which may not need any adjustment once that’s nailed.

Ok, I will try that suggestion and persist.

Last question, for now. How is it possible to have found a generic profile for my particular display that has a media white point tag set to 6500K??? How did the creator of this profile attain this media white point? If I can find an answer to this question I would be very content.
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digitaldog
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« Reply #13 on: July 31, 2010, 01:59:09 PM »
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Quote from: angelnavarrophotography
Ok, I will try that suggestion and persist.

Last question, for now. How is it possible to have found a generic profile for my particular display that has a media white point tag set to 6500K??? How did the creator of this profile attain this media white point? If I can find an answer to this question I would be very content.

There are editing app’s for profiles that presumably could do this.
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Andrew Rodney
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angelnavarrophotography
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« Reply #14 on: July 31, 2010, 02:01:50 PM »
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Quote from: digitaldog
There are editing app’s for profiles that presumably could do this.

Can you name one? ColorThink does not and neither does ColorSync.
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digitaldog
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« Reply #15 on: July 31, 2010, 03:02:53 PM »
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Quote from: angelnavarrophotography
Can you name one? ColorThink does not and neither does ColorSync.

ProfileEditor, part of ProfileMaker Pro is one example.
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Andrew Rodney
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angelnavarrophotography
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« Reply #16 on: July 31, 2010, 05:13:14 PM »
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Quote from: digitaldog
ProfileEditor, part of ProfileMaker Pro is one example.

Checked out ProfileEditor and a dongle is required to use. Do you any means of editing this media white point tag from 5000K to 6500K? I tried HexEdit, Resourcer, ProfileMaker, ColorThink, ColorSync, TextEdit, SpectraView, BlueEye, and nothing gets into the tag and edits. If I send you the profile, could you make the small change?
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WillH
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« Reply #17 on: August 02, 2010, 03:59:27 PM »
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Quote from: angelnavarrophotography
WillH,

I re-read and discovered I misread your suggestion. Your suggestion was to observe the information, not to fix the problem. Please accept my apologies. The dialogue box I am including as an attachment. When I dropped down to D65 it read x=.3127 and y=.3290 - not sure what that means but I thought you might. All I can say is that anything red on my display looks orangy/red due to "HuhHuh??"

Those numbers are D65 - which proves Photoshop is getting the correct white point for the display via the ICC profile. If your images look OK when you aren't doing a softproof, and have problems when you are, then I would suggest you look into the printer profile that you are using and make sure that doesn't have any issues.
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Will Hollingworth
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NEC Display Solutions of America, Inc.
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