You need to actually embed Adobe RGB or Gray Gamma 2.2 into the target to get the proper printed values.Then linearize, and then your curve will print linear for any image embedded with a gray gamma 2.2 space (specifically Adobe 1998 and Grey Gamma 2.2)best,WalkerOn Dec 6, 2016, at 8:20 PM, nigglefish@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:I am using PrintTool and QTR on Mac OSX. I have been creating and linearising curves but I am a bit unsure of how to proceed to actual printing. I'm sure I can work it out through trial and error, but that won't help me understand the underlying color management concepts any better. So I thought I would describe what I have done and ask how I should proceed. (A few details have been simplified.)
1) I created a .quad QTR curve using my own software and installed it.
2) I created an 8-bit 18 patch grayscale target image in Gimp with each patch having a value 15 units higher than the last (0, 15, 30, 45, ..., 255). When I open this in PrintTool it reports the embedded profile as 'untagged'.
3) I printed the target using PrintTool selecting 'No color management'. I used the QTR driver and selected my curve in the QTR print settings.
4) I measured, adjusted, linearised and printed many times.
5) I finally printed the target and measured linear lightness readings across the patches. That is, after measuring with a ColorMunki the difference between each adjacent patch in terms of L* readings was (just about) equal.
I'm happy to have gotten to this point, but I'm not sure if I have been headed to the right place or not. Maybe the desired readings for each patch should have been different? I don't know. I now have a photo I want to print. It reports an embedded profile of 'Adobe RGB (1998)' in PrintTool. I'm not sure what settings I should choose in terms of color management now to print that. I am assuming I should select 'No color management' again. But again I don't know.
So I have two questions:
1) Given my target and printing options what lab readings should I be trying to get for each patch?
2) Once I have achieved those readings what setting should I use to print a photo with an embedded profile.
Happy for any other information, background or guidance. Thanks in advance.
Message
Re: [QuadtoneRIP] Color Management Confusion
2016-12-07 by Roy Harrington
?? Targets for QTR linearization or for ICC profile creation are ALWAYS printed without
--
Color Management. "No Color Management" specifically ignores the embedded profile
even if one exists. So tagging targets has no effect if printed with NoCM.
QTR linearization creates a straight-line graph of K-values vs L--values, where K is the whole
range from K=0 (white) to K=100 (black) and L ranges from dMin to dMax. This is quite
different from Gamma 2.2 which is not a straight-line.
There are numerous ways to deal with this difference and you'll see that everyone's got
a favorite that they "swear by". The basic ones are:
1) get used to it, edit your files till they produce the print you like.
(might be surprising but I bet this is the most used -- after all that's what we did in darkroom)
2) add correction curve in Photoshop. It's a very convenient idea for Windows.
See www.paulroark.com for info on this.
http://www.paulroark.com/BW-Info/Eboni-4-Plus.pdf page 16 has a very good description
of the issue and of the solution
3) make ICC profile for soft-proofing. basically what you do here is edit your image under
soft-proofing so that output print matches what you want. nice for Windows but your files
are now targeted for a specific printing output
4) finally there's the standard color management approach. Make an ICC profile and print
with it. On a Mac with Print-Tool this is by far the easiest and in a sense the "standard" way.
With nice linearized QTR profiles the generic "QTR driver Gray Matte (or Photo) Paper"
ICC profiles do quite well but a customized one with all the QTR driver blending selections
etc is the best. Personally I like this the best but it's less convenient for PCs. Also if you are
used to #1 above you'll find it disconcerting at first because you have to re-get-used-to-it.
Roy
On Tue, Dec 6, 2016 at 6:20 PM, 'forums@...' forums@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote: