Re: UV Brighteners
Re: UV Brighteners
- Subject: Re: UV Brighteners
- From: Joel <email@hidden>
- Date: Mon, 12 Feb 2001 14:51:16 -0600
Les Schofer wrote:
I profile using the Colormouse with CB Matchbox 4.0. On my first attempt
profiling a target from my Kodak 8650PS in CMYK I got a real decent
result. When I tried to develop a profile for its RGB (CMY) output I gor
significant shifts to magenta in the lighter grays, and over to cyan in
some of the darker ones. Several days ago I got the idea that this may
be because I was printing the RGB files with the media's UV coating, as
this is how I print all the prints I deliver to clients. When I proof
CMYK output, however, the ribbon's 4th patch is black, and no UV coating
is laid down. Your excellent explanation hints that the UV cating could
be skewing the readings the Colormouse takes, whereas its presence is
undetectable to the eye. Do you think or have specifid experience that
this could be the problem?
Well Les, the excellent explanation on UV came from Chris Pearson at
ColorSavvy (they deserve the plug for their good service after all).
As for the graduated greyscale color tints that's not really
necessarily or by chance a UV thing. It's more likely an inkjet
thing; mainly how your RIP or print software interprets the ink mixes
used by the printer's screening pattern (often a form of stocastic or
other) in order to perceptually render greyscale. UV brighteners are
a coating (substrate) incorporated in the media you are printing on.
Some print characterization packages (like PrintOpen 4.0) compensate
for florescence as an option when creating the profile if you are
using a spectro or device which generates white light. The CM2S
spectro, as I understand it from Savvy, does not generate white
light, so florescence is not an issue in the readings thus making the
source data fine and the profile adjusting a bit more complicated if
you happen to recognize a florescence issue - often a blue or yellow
shift. Often using canned or uncompensating profiles will cause
tints, most noticably in the grescale, especially if used on media
other than that which it was written for: hereintoafter referred to
as third party media.
For a good read (and more sense than from me!) here, have a few URLs on
http://www.praxisoft.com/color/getstarted.html
http://www.profilecity.com/site.asp?menu=knowledgebase&file=knowledgebase.asp
this list goes on and on. I can't find my ICCabc url so I'll just
send you the PDF's outside the list.
caio
--
joel johnstone - designtype
Winnipeg Manitoba Canada
email: work: email@hidden
color geek in residence, reality notwithstanding