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Author Topic: Gretag i1Match = less Dmax  (Read 4000 times)
andyheb
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« on: July 03, 2007, 12:42:26 PM »
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Hi there

I'm printing with an EPSON 4800 mostly on Hahnemühle PhotoRag. Since a few weeks, I can make my own ICC profiles using a Gretag eye-One and i1Match.
So far so good and i'm very pleased with the colors I get now.

But something ist really strange and drives me crazy: Regardless which (matte) paper I use, I always get lighter blacks with the i1Match-Profiles than the canned profiles of the paper manufacturer. Here are the numbers for PhotoRag:
Canned profile by Hahnemühle: Dmax = 1.65 - 1.67
Gretag profile (ICC Spec. 2 & 4): Dmax = 1.60

Seems not so much, but everything printed with the canned profile has less "gray fog" and pops a bit more. When I measure the darkest patch on the profiling chart, it is also much darker then the deepest black patch printed with an i1Match-Profile.

As you can imagine, i'm not really happy after spending so much money for my own profiling solution just to figure out, that the most important thing to me (Dmax) ist getting worse than before.

Has anyone faced this problem already?
Is there a solution (ideally without spending more money!)?

Thanks in advance!
Andy
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madmanchan
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« Reply #1 on: July 03, 2007, 01:48:11 PM »
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Questions:

- which rendering intent are you using?

- are you using black point compensation?

- fill a canvas with RGB = (0,0,0) in Photoshop and then do a conversion (Edit menu -> Convert to profile) to your i1-created profile. Then use the color picker and read out the converted RGB values. what are they?
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andyheb
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« Reply #2 on: July 03, 2007, 02:40:39 PM »
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Quote
Questions:
- which rendering intent are you using?
- are you using black point compensation?
- fill a canvas with RGB = (0,0,0) in Photoshop and then do a conversion (Edit menu -> Convert to profile) to your i1-created profile. Then use the color picker and read out the converted RGB values. what are they?
[a href=\"index.php?act=findpost&pid=126261\"][{POST_SNAPBACK}][/a]

Answers:

Rendering intent = Perceptive
BPC = tried OFF an ON, makes no difference on the print

ICC-Profile for PhotoRag and EPSON 4800 Spec. Version 2 by i1Match:
RGB (0,0,0)  perceptive, BPC OFF = 12, 11, 11
RGB (0,0,0)  relative colorimetric, BPC OFF = 6, 6, 12
RGB (0,0,0)  perceptive, BPC ON = 28, 25, 24
RGB (0,0,0)  relative colorimetric, BPC ON = 12, 13, 18

ICC-Profile for PhotoRag and EPSON 4800 Spec. Version 4 by i1Match:
RGB (0,0,0)  perceptive, BPC OFF = 9, 9, 8
RGB (0,0,0)  relative colorimetric, BPC OFF = 6, 6, 12
RGB (0,0,0)  perceptive, BPC ON = 19, 17, 16
RGB (0,0,0)  relative colorimetric, BPC ON = 12, 13, 18

ICC-Profile for PhotoRag and EPSON 4800 created by Hahnemühle:
RGB (0,0,0)  perceptive, BPC OFF = 0, 0, 0
RGB (0,0,0)  relative colorimetric, BPC OFF = 5, 10, 19
RGB (0,0,0)  perceptive, BPC ON = 30, 27, 28
RGB (0,0,0)  relative colorimetric, BPC ON = 4, 11, 20

These numbers show really good what I mean. Only the Hahnemühle-Profile renders black as RGB(0,0,0) when using the perceptive RI without BPC.
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digitaldog
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« Reply #3 on: July 03, 2007, 03:27:58 PM »
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A lot of these canned profiles are edited after the fact to this kind of rendering (some think it looks better, others not). It might also be a difference in print driver settings, hard to say. If you had an editor, you could whack the blacks down.

Also check both profiles to see how they soft proof this dmax (using paper white, ink black). Do both profiles show what you're actually getting?
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Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
madmanchan
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« Reply #4 on: July 03, 2007, 06:23:32 PM »
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Andy, try using the approach described on the page below to change the perceptual gamut mapping method to LOGO Chroma Plus:

http://people.csail.mit.edu/ericchan/dp/i1...ping/index.html

Then try re-building your profile and see what you get.
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andyheb
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« Reply #5 on: July 04, 2007, 04:06:17 PM »
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Hi Andrew,
Hi Eric

First, thanks for your answers.

@Eric: switching to the "ChromaPlus" Gamut Mapping, as described in your tutorial, did it! Now 0,0,0 black is really rendered as 0,0,0 using perceptual rendering intent and BPC OFF. Also does the "Classic"-Mapping, but I like the ChromaPlus more for the things I print.
And my first test print confirms that the issue is solved. I get a Dmax of 1.63 measured ~30 minutes after printing. I guess, when the print is completely dry, it will be get up to 1.65-1.67.

Thank you very much for your help!
Did you know that this would solve it or did you guess?

Andy
« Last Edit: July 04, 2007, 04:07:42 PM by andyheb » Logged
madmanchan
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« Reply #6 on: July 05, 2007, 10:38:24 AM »
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Hi Andy, glad to hear this resolved the issue. I had previously discussed this same issue with another GM i1 user. This fix was proposed by a tech support rep at GM. The lower d-max is a "known issue" with LOGO Colorful (the default in Match). Good thing other options are accessible!  
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pherold
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« Reply #7 on: July 06, 2007, 06:41:09 PM »
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It is also possible to get a little more depth from your blacks in the measurement itself.  You would need a spectrophotometer that has a polarizing filter on it.  This helps to filter out any stray light that  would lighten the measurement of blacks and is especially useful for matte papers and canvas.  (Unfortunately, this is where your hope of an inexpensive fix is going to be dashed.)  Spectroscan tables ran about $5000, when GM was still making them.  We still use them at Chromix for purposes like this.  This is one of those rare incidences where having a custom profile built by someone with the right equipment can be better than owning your own.

-Pat Herold
CHROMiX Tech Support
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-Patrick Herold
  Tech Support
www.chromix.com
digitaldog
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« Reply #8 on: July 06, 2007, 07:03:14 PM »
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Until something ever comes that can provide the same operations, I'm keeping my Lino XY/T as well as a DTP-41UV/T  (the T being the important once every two years of use functionality).
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Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
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