Re: CompassProfile - help creating greyscale profile for RGB device.
Re: CompassProfile - help creating greyscale profile for RGB device.
- Subject: Re: CompassProfile - help creating greyscale profile for RGB device.
- From: Jim Rich <email@hidden>
- Date: Tue, 08 Apr 2003 21:15:12 -0400
On 4/8/03 3:33 PM, "Reed Photo-Imaging" <email@hidden> wrote:
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I am sure this has been covered, but a search of the archives was futile. I
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appologize for rehashing a potentially previous subject.
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We are attempting to generate a greyscale profile for our LightJet printers.
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These are photographic printers using RGB lasers to expose photographic
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emulsions. We print both chromogenic and real black and white materials. Here
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is the rub: Although there are several workarounds for creating grey swatches,
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the software refuses to recognize the need to evaluate them as grey, so the
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resulting profiles attempt to force color back into the image file. This
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results in extreme color posterization, and any hope of tonal integrity is
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lost.
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Is it possible to achive a decent greyscale profile with this software, or
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should we investigate another product. Praxi's tech support was unable to
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resolve this issue.
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John Harris
John,
One method to deal with grayscale profiles is to use the Photoshop Color
Settings options that allow you to create grayscale working spaces and
printer profiles. There are claims that some programs grayscale profiles
but for me seeing is believing.
Another option is to use an RGB profiled workflow with tools like Hue & Sat
set to -100 Saturation to avoid too many conversions.
I don9t work with LightJets every day, but it sounds like your Light Jet
needs a tool like a rip to handle grayscale profiles more efficiently.
And FYI, here is what I have posted previously about grayscale printer
profiles.
In Photoshop there are 13 different halftone values you can measure with
a instrument, such as a densitometer or a spectrophotometer. These values
are based on the custom gray scale options in the Color Settings dialog
box. After the values are measured, they are keyboarded into the Photoshop
Gray Color Setting and saved as an ICC grayscale printer profile. Here are
the technical details.
1. Create a 13-step test target file of patches with halftone values of 2%,
4%, 6%, 8%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%. This test
target can created in Photoshop or in a page layout program. Then print them
to your printer. Check to be sure you are printing just black ink or toners
and not color.
2. Measure the values from the printed test file with a densitometer or a
spectrophotometer that uses software that can convert the CIE values to
halftone percent dot values.
3. In Photoshop, go to the menu and select Edit/Color Settings/Working
Spaces: Gray. Use the Gray pop-up menu and scroll to Custom Dot Gain.
4. Enter a name for your custom dot gain and key board in the 13 grayscale
values into the appropriate data entry boxes. Enter OK.
5. To save the dot gain curve use the Grayscale pop-up menu Save Gray
option. Be sure to use the extension .icm or .icc as you save the profile in
the ColorSync folder (Mac) or Color Directory (Windows).
6. The Working Space will display your custom setting in the Gray pop-up
menu. Click OK to begin working.
Now your grayscale printer profile is ready to be used with Photoshop.
Good Luck
Jim Rich
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