On Saturday 08 August 2009 07:23:49 pm Hal V. Engel wrote: > On Saturday 08 August 2009 03:52:25 pm John Culleton wrote: > > On Saturday 08 August 2009 04:54:09 pm Hal V. Engel wrote: > > > On Saturday 08 August 2009 12:07:59 pm John Culleton wrote: > > > > On Saturday 08 August 2009 11:58:40 am Gregory Pittman wrote: > > > > > On 08/08/2009 11:57 AM, John Culleton wrote: > > > > > > On Friday 07 August 2009 07:19:29 pm John Culleton wrote: > > > > > >> LSI is enforcing a rule that total ink coverage of any > > > > > >> CMYK color cannot exceed 240% The usual example is > > > > > >> rich black. > > > > > >> > > > > > >> 1. Can this be a problem in Scribus? > > > > > >> 2. If so, how does one detect/fix such overcolored > > > > > >> areas? > > > > > >> > > > > > >> I presume that none of the standard colors exceed this > > > > > >> limit. But I worry about graphics from e.g., Gimp > > > > > >> which are RGB converted to CMYK when Scribus writes > > > > > >> the file. > > > > > > > > > > > > To further illuminate the question, these are the > > > > > > recommended values whan using Photoshop: > > > > > > ------------------------ > > > > > > Engine: Adobe (ACE) > > > > > > Intent: Relative Colorimetric > > > > > > Use Black Point Compensation: Yes > > > > > > Use Dither: Yes > > > > > > ------------------------------- > > > > > > and > > > > > > ----------------------------------- > > > > > > Ink Colors: SWOP (Newsprint) > > > > > > Dot Gain: 25% > > > > > > Separation Type: GCR > > > > > > Black Generation: Medium > > > > > > Black Ink Limit: 100% > > > > > > Total Ink Limit: 240% > > > > > > UCA Amount: 0% > > > > > > ------------------------------- > > > > > > for the custom CMYK settings. > > > > > > > > > > > > Perhaps there is an ICC profile that can take care of > > > > > > all this. > > > > > > > > > > I don't know that there are any color sets that come with > > > > > Scribus that will exceed this. Of course, we get some > > > > > list questions from some who think that they want all the > > > > > CMYK saturated, but obviously don't understand the > > > > > printing issue. > > > > > > > > > > What it does suggest, though, is that one of the things > > > > > the Preflight Verifier could do would be to check for ink > > > > > limits. Maybe you could file an RFE. > > > > > > > > > > Not sure how they might imagine someone specifying > 100% > > > > > Black...seems that would be kicked out by the printing > > > > > equipment. > > > > > > > > > > Greg > > > > > > > > > > _______________________________________________ > > > > > scribus mailing list > > > > > scribus at lists.scribus.info > > > > > http://lists.scribus.info/mailman/listinfo/scribus > > > > > > > > Consider the image from Gimp that has black on it. That is > > > > RGB 0 0 0. What would Scribus change it to in CMYK? > > > > > > There seems to be some misconceptions here. CMYK is a > > > subtractive color space so higher values mean more ink (if > > > you are talking about a printer). The K ink in a CMYK system > > > is used as a substitute for higher levels of process gray (C > > > = M = Y) to create darker tones and reduce ink load for the > > > same darkness. Many printer/ink/paper combinations can handle > > > total ink levels much higher than the 240% talked about above > > > but some can not and some can not handle even 240%. > > > > > > The darkest blacks on most printers are a combination of K > > > plus C and M (sometimes called rich black). In addition on > > > many modern ink jet printers the "black" ink has a yellow > > > tint that is intended to allow these very dark blacks without > > > causing a hue shift because of the added C and M ink (IE. to > > > keep the resultant black neutral). The normal operation for > > > these printers is to always mix some C and M ink with the K > > > ink to shift the hue toward neutral even for lighter grays > > > although for the very lightest grays this may not be needed > > > because the white point will be shifted toward blue (IE. away > > > from yellow) because of the "whiteners" used in many papers. > > > > > > All of this is very device specific, meaning specific to a > > > printer/paper/ink/work flow, and the only way to insure that > > > you are doing the right CMYK separation for your device is to > > > use the correct ICC profile for the device in question. > > > These profiles will have an optimized GCR setup and also have > > > proper ink limits so that there is no over inking and there > > > are proper transitions to the K ink as well as proper use of > > > C and M inks to keep grays and blacks neutral. > > > > > > Hal > > > > > > _______________________________________________ > > > scribus mailing list > > > scribus at lists.scribus.info > > > http://lists.scribus.info/mailman/listinfo/scribus > > > > LSI wants the SWOP profile but also enforces the 240% rule for > > cover files. They have an ink and paper combo that requires > > this limit. The usual way to make sure that their specs are met > > is through Photoshop. I am looking for a Scribus way. > > If LSI is so picky about this perhaps they can give you a profile > that insures that you produce separations to their > specifications. But if that is not the case then create a > profile that uses the SWOP characterization data set but that has > a 240% ink limit instead of the default for SWOP (320% for the > newer profiles and 300% for the older ones). This can be done > using ArgyllCMS. There are threads on the ArgyllCMS email list > about how to get and use the SWOP characterization data. > Setting a custom ink limit is easy to do when you get to that > part of the profile creation process. > > Hal > I'll follow up on that. The issue may revolve around rich black.
-- John Culleton Create Book Covers with Scribus/e-book $5.95 http://www.booklocker.com/books/4055.html
