Re: GRACoL Press Sheets & Dot Gain Curves
Re: GRACoL Press Sheets & Dot Gain Curves
- Subject: Re: GRACoL Press Sheets & Dot Gain Curves
- From: "RS" <email@hidden>
- Date: Fri, 15 Jul 2005 11:24:23 -0700 (PDT)
- Importance: Normal
In my previous post I did not distill this issue into its key elements to
illustrate why this is an important issue to other ColorSync List readers.
Here's a summary. Bret, please add/modify.
When commercial printers wanted to follow a specification for printing (be
it SWOP, GRACoL, etc.), they aimed to match two measured variables--ink
density and tone value increase (TVI, or dot gain) at 50%--for each
four-color process ink. In its efforts to develop the TR004 specifiction,
GRACoL found significant variation in the visual appearance of press
sheets when this density/TVI-weighted method was employed in test runs
done at a number of printers throughout the country.
Don Hutcheson and Larry Warter (see the articles noted in previous posts)
present an alternate approach in which maintaining gray balance throughout
the tonal range is given priority over matching a specific density and
TVI. When this gray balance-weighted method is employed they find a better
visual match among press sheets from printers across the nation. GRACoL is
now pursuing to refine and document this approach.
email@hidden
> Bret,
>
> Many thanks for suggesting Don's presentation. It made perfect sense after
> speaking with Dick Presley of Kodak Polychrome Graphics and reading Don
> and Larry Warter's article "GRACoL Guidelines for Realistically Applying
> Color Management" in the May/June 2005 IPA bulletin
> (http://www.ipa.org/pdf/J-05-GRACol-Guideline.pdf). Don and Larry's
> article puts in prose form the ideas outlined in the presentation on the
> GRACoL website.
>
> After reading Don and Larry's compelling argument that gray balance is
> paramount, I'm no longer as concered with matching specific TVI numbers
> over a range of tones.
>
> In the case anyone is interested, Dick sent me the following TVI values
> from certified IPA RoundUp press sheets that came from a test at Integrity
> Graphics in Windsor, CT. According to Dick, this test run was one in which
> gray balance was given greater weight when making press adjustments.
>
> Yel Mag Cyn Blk
> 25% 17 15 10 19
> 50% 19 17 16 21
> 75% 11 10 10 14
>
> email@hidden
>
>
>> Check out Don Hutcheson's presentation "The Quest for Real Print
>> Standards"
>> at www.gracol.org DTR004 and the GRACoL spec are likely to change in
>> the
>> near future. Don's method has been used on several GRACoL pressruns,
>> with
>> promising results. L. P. Thebault will be doing the next GRACoL run next
>> week. We have used this method, and we like what we have seen.
>>
>> Bret Hesler
>> L. P. Thebault Company
>>
>>
>>> Date: Thu, 14 Jul 2005 05:24:50 -0700 (PDT)
>>> From: "RS" <email@hidden>
>>> Subject: GRACoL Press Sheets & Dot Gain Curves
>>> To: email@hidden
>>> Message-ID: <email@hidden>
>>> Content-Type: text/plain;charset=iso-8859-1
>>>
>>> GRACoL 6.0 provides a helpful chart of dot gain values CMYK inks at 50%
>>> for various paper and line screen combinations. It lacks, however, dot
>>> gain values at points other than 50%. I'm documenting the current dot
>>> gain
>>> curve of a press and am interested in doing a more thorough comparison
>>> of
>>> this data set, and I'm curious if anyone here has seen (or measured
>>> themselves) dot gain values of a GRACoL DTR 004 sheet in steps of 5% or
>>> 10%. (Although I've not seen one, I'm assuming the GRACoL sheet has
>>> step
>>> wedges of each color).
>>>
>>> While the press with which I'm working may print within GRACoL's dot
>>> gain
>>> range at 50%, I'm interested in seeing how much its gain differs in the
>>> quarter- or three quarter-tones. I just want to be certain there isn't
>>> anything wonky going on with the press at points other than the
>>> midtones.
>>>
>>> email@hidden
>>>
>>
>>
>
>
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