Re: Epson7000: Absorption/ReflectanceReadings
Re: Epson7000: Absorption/ReflectanceReadings
- Subject: Re: Epson7000: Absorption/ReflectanceReadings
- From: email@hidden
- Date: Sat, 30 Dec 2000 11:30:09 EST
In a message dated 12/29/00 8:24:16 AM, email@hidden writes:
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I am attempting to tweak an ICC profile using an Epson 7000 using
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Generations inks, and a coated watercolor sheet. I had Andrew do a
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profile for me, and it's very "neutral" but it tends to moosh up in the
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90/95/100% areas. I'm using CustomColorICC to tweak his profile. Several
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questions have come up in this process:
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1. Even though this sheet is coated, is there a possibility that the
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inks would absorb "more" in these more saturated areas? I built a curve
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to try to alter this and it's worked pretty well. I tried to isolate
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only the 90-100 areas.
This is likely to be caused by the RGB driver's sharp CMY gray to K black
transition in this range; a good CMYK RIP would do offer more control of
this...
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2. Why do profiles have both a name and a description? It seems that
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sometimes a profile is known by one or the other in a pull-down menu.
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What's the purpose in this two-pronged approach? It seems only to risk
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confusing matters.
Yes, its a problem with the ICC standards, and the best current approach to
dealing with it is to make sure both are identical...
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3. I also added Digital Swatchbook to the mix this week. After setting
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it up and calibrating it, I notice that even though my 100% black chip
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in the 21-step wedge LOOKS totally black, the reading from the
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spectrophometer reads out at about 31/32/35 RGB.
Thats a pretty typical L value for a black patch on WC paper...
I would think it would
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be definitely 0/0/0, because the black is so saturated. Just to check,
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we read also a glossy stock with a black chip, and also got about
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30/30/30 value in the black.
This is not suprising. Glossy stock can have black L values below 20, but
that depends on a number of factors...
This seems to devalue all the other reading
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that we got along the wedge, although the upper values seem to coincide
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more with the RGB value from the InfoPallette. The problem seems to
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start when you get darker than about 80-85%. I tried to find a way to
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manually "force" my blackest black to a "0/0/0 reading" but could not
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find a way.
This is not the issue, or the solution; controlling your black generation is
the best solution (see above) or avoiding K blacks by setting your images
darkest areas to be less than black (oddly enough) can improve things on
water color papers by avoiding K only blacks and instead using dark CMY mixes
right up to the darkest tones in the image, to avoid the K transition
entirely.
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Any insight on these three issues would be appreciated. Thanks in advance.
Best of luck with your issues.
C. David Tobie
Design Cooperative
email@hidden