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>
[mailto:argyllcms-bounce@xxxxxxxxxxxxx] *On Behalf Of *Yves Gauvreau
*Sent:* Friday, July 5, 2019 6:16 PM
*To:* argyllcms@xxxxxxxxxxxxx <mailto: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
<https://www.argyllcms.com/doc/Scenarios.html#LP3>*" 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
