I'm not sure that is what the '-c' option was intended for and suppose only
Graeme can let us know if this would work. In my own workflow, I have only
used it to prepare a final patch set from a preliminary profile.
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Graham White
Sent: Sunday, July 7, 2019 10:42 AM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Testing my new printer
Well, I have just looked up the targen man page, and there is an option -c
which allows you to specify a profile (ICC or MPP), and this profile will say
which colour space the patches should be generated it. Thus, it can be sRGB, or
Adobe RGB, or whatever you
want: you're not limited to
sRGB.
Graham
On Sun, Jul 7, 2019 at 2:18 PM <graxx@xxxxxxxxxxxx> wrote:
Yves,
To my humble knowledge, targen generates “device channel” RGB or CMYK
or Grayscale, I fail to see how it could its “Device values” be
anywhere outside of a “dependent”, rigid, cold, “mathematical” space?
Suppose a scale of 0% to 100% on each CMYK channels or 0 to 255 RGB or
0.00 to 1.00 RGB, then, how could these numbers relate to CIE Lab
colors? How do you see those colors “belonging” or “refering” or
“describing” sRGB or AdobeRGB or ProPhotoRGB or any other
“independent” color space? RGB = 255,0,0 denotes “Red” but that’s all
it can denote, not an “sRGB Red” or “AdobeRGB Red”? But I confess I am
not a expert at Argyll’s myriad of options…
To explore “more volume”, as you suggested, and according to my humble
understanding of color management, the use of CIE Lab seems the only workable
approach, such as creating a number of Lab colors that would be outside of
some Destination gamut, to then convert them to the Destination using both
approaches, with and without a “Source” optimization.
Then, as you noted, Yves, measure the resulting colors of both sets and then
proceed to whatever analysis one finds relevant.
That approach, to me, appears sensible and ought to yield interesting
findings.
Best / Roger
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx>
On Behalf Of Yves Gauvreau
Sent: Saturday, July 6, 2019 2:28 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Testing my new printer
Roger, Alan, List,
It seems that targen create a set of colors totally enclosed in sRGB
colorspace. I even tried to use ProPhoto as a pre-conditioner (-c -A xx) to
see if it resulted in something bigger, no chance. Is there a way to explore
more volume (gamut) then just sRGB?
As for an objective method of evaluation the more I look at this the more I
think we'll need a patch set, maybe in LAB, that presents many color outside
of the sRGB gamut say 40-50% and say 20-30% still outside of the output
gamut. Then you print these patches using both method, measure the resulting
colors of both sets and then proceed to whatever analysis you find relevant.
I would think some delta error measures and some statistical measures would
be a good start.
Yves
On 7/6/2019 11:14 AM, graxx@xxxxxxxxxxxx wrote:
Yves, Alan, List,
Moi aussi, je réfléchis à une méthode objective d’évaluation.
There has to be a difference between “image-gamut based” conversion and
“color space” or “specific color space” conversions. The difference, however,
is not easy to analyze.
(Have to give it better thought…)
I am running into the same problem as Yves’s original issue, what is it that
we’re getting (presumably of ‘extra’ value) when creating custom-tailored
printer profiles in Argyll?
As some of you may know, I’m experimenting with Epson EnhanceMatte paper
these days, on my humble inkjet printer, and, the moment, I am in the final
stage of characterizing the whole thing with an IT8.7/4 target in my hands,
ready to measure and generate an Output profile for.
Q1: do I want to flip the switch on some ‘Source’ space optimization? Such as
‘sRGB -> EnhanceMatteCMYK’?
Q2: Once I do, how do I go about finding the difference?
I figure I’m going to need to create some kind of synthetic image to be able
to make the differences come out? My take is that A) colors that are already
well within gamut, such as skintones, blue skies, most foliage and grays are
all going to be mapped pretty much 1:1 but B) colors that are out-of-gamut
have to suffer some kind of compression.
I think I remember seeing some visualization of this? But I’d like to see in
on a graph, in Excel. Love Excel….
Best / Roger
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx>
On Behalf Of Yves Gauvreau
Sent: Saturday, July 6, 2019 6:33 AM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Testing my new printer
Alan,
my printer is the same as yours (Pro-1000) and I used a letter size sheet of
Hahnemuehle fine art baryta paper. I use the same test or standard image as
you do every time I want to have an idea of what a paper can give me. Now I
do this part a bit differently to save ink.
In the docs it is mentioned this: "When images are stored in large gamut
colorspaces (such as. L*a*b*, ProPhoto, scRGB etc.), then using the
colorspace gamut as the source gamut for gamut mapping is generally a bad
idea, as it leads to overly compressed and dull images. The correct approach
is to use a source gamut that represents the gamut of the images themselves."
Since I print just as you do most of the time, from Lightroom I wondered if
my prints where impacted in the way the doc mention because Lightroom uses
the ProPhoto RGB colorspace by default, and because this effect seemed to be
barely noticeable on the relatively large gamut papers I use most of the
time. I notice thought that on some papers with a smaller gamut, the result
are much less interesting or kind of dull but again all this is subjective.
I'm not sure but I think Graeme mentioned to someone about his method that
folks at Adobe for example may very well do something similar without letting
you know about it. I know that Adobe is adding a curve to there Adobe
Standard profile on each raw conversion Lightroom or ACR does, it makes the
image "look" better but at the expense of dynamic range (reduction) and many
times it increases clipping of the highlights and it also reduces highlight
details in many case.
So I wonder if someone here as a method or suggestion of evaluating all of
this more objectively and or accurately then just comparing standard prints
visually?
Yves
On 7/5/2019 8:42 PM, Alan Goldhammer (Redacted sender agoldhammer for DMARC)
wrote:
You do not say what the make of the printer is and what type of paper you
will be printing on. Most RGB printers are well behaved and I do not see the
need to use exotic approaches to printing. I print directly from Lightroom
on my Canon Pro-1000 as it is the most convenient way to print as one only
needs to set things up once and then save the preset. I do my profiling
using Argyll for the papers I print on. I evaluate profiles visually using
this test print:
http://www.outbackphoto.com/printinginsights/pi049/essay.html which has ;
various standard images that have been used for some years now. I do soft
print in Lightroom but only to correct for certain colors and hues as soft
proofing for out of gamut colors is notoriously poor.
Alan
From: argyllcms-bounce@xxxxxxxxxxxxx
[mailto:argyllcms-bounce@xxxxxxxxxxxxx] On Behalf Of Yves Gauvreau
Sent: Friday, July 5, 2019 6:16 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Testing my new printer
Hi,
I started testing my new printer with an image that as colors outside the
gamut of the paper as per ColorThink 2.3.3 to see if there would be a benefit
in using the "Image dependent gamut mapping using device links" method and
printing from Photoshop and I don't see any difference at least visually. I
know this is amateurish to say the least.
So is there a mean to evaluate this process (using the image gamut) more
"properly" and more exactly?
Thanks
YG
