Re: U.S. Web Coated (SWOP) v2 always produces blues that shift?
Re: U.S. Web Coated (SWOP) v2 always produces blues that shift?
- Subject: Re: U.S. Web Coated (SWOP) v2 always produces blues that shift?
- From: Steve Upton <email@hidden>
- Date: Mon, 2 Jul 2007 15:34:17 -0700
At 2:31 PM -0600 6/27/07, Andrew Rodney wrote:
>Here's one quote from an industry expert who believes that the TR001
>specification as reflected in the U.S. Web Coated (SWOP) v2 profile built by
>Thomas Knoll in Photoshop always produces a blue shift. I was hoping some
>here with experience with this process could comment. The profile he's
>supposedly comparing is one that is based on G7 spec:
><snip>
>Comments?
>
>Ideally I'd like to put this to a test using something a bit more reliable
>and empirical than simply looking at CMYK numbers from a file that someone
>separated. Anyone have a proofing device or press that conforms to TR001
>that would be willing to run a test?
This sounds like an overprint (secondary color) issue.
In the G7 press gray balance work we've been doing - including the development of IDEALink Curve to perform the plate curving - I have noticed something important.
No matter how well you hit typical press aims such as solid ink density, TVI, etc., curving plates and handling other factors like SID & TVI at press time does NOT necessarily hit the secondary colors.
Put another way, people who hit all the (obvious, primary) requirements of SWOP or GRACoL and also use G7 to setup their press may still miss on their red, green and blue colors.
What this really comes down to is trap. How well are inks getting along on press? If cyan won't stick to magenta (or vise versa, depending on laydown order) then overprints for blue won't look right. Even IF the inks are 'ISO' certified to be the right hue, the dot gain is correct, solid ink densities are correct, paper color is in range, and so forth.
One place proofing systems have historically fallen short is they either don't simulate real-world trap at all (think Matchprint) or they do, but not the same way the actual press behaves. Recall that the US Sheetfed profile has been based on a Matchprint proof up until now... I'm not sure if Czar Knoll adjusted the profile to account for this shortcoming of Matchprints or not - I would not be surprised if he did, being the rather smart guy that he is.
Anyway, the publication of new data for GRACoL and SWOP (as well as all the hard work the folks at FOGRA are doing) is a big boon not just for RIP-driven proofing systems but also the profiles that we will see in Adobe apps. BUT even then, it's not always easy to hit the real-world numbers of the GRACoL or SWOP runs on press without having a good relationship with your ink vendor.
So... if a TR001-separated job turns out with funny blues or reds, check to see how they did on press with blue and red relative to TR001...
remember, it's peanut butter THEN jelly, not the other way around...
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
o ColorGear ColorThink ColorValet ColorSmarts ProfileCentral
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