3D printed bracket for Colormunki and question about pointy end of my profile

[soswow]

Hello,
This is my first post, so please no big stones (small stones I can handle).
I've purchased Epson et-8550 and collected a mountain of different papers. Then I found a very good deal (lucky?) for an old Colormunki Photo device. I've been using ccStudio all day long to make custom profiles. Learned a ton by making even more mistakes and by listening Keith Cooper :-D.

The latest paper I was trying to make a profile for is giving me trouble. When I make a profile using ccStudio resulting shape in ICC viewer (on mac) looks strange - its bottom part is pretty flat and is not as pointy as some of the stock profiles. (one of the gifs shows it)

Lately, I've got brave enough to try Agryll. I thought - the more patches - the better. I tried to go crazy and crammed 572 patches into A4. To be very accurate with measurement I've designed and printed a special bracket for Colormunki. I just released it for free if someone wants it - BRACKET FOR COLORMUNKI PHOTO
Eventually, I went with the normal patch number of 210 and printed with `-h` command.

The resulting profile shape looks smooth with a pointy black point, but when I compare it to other profiles (stock and made with ccStudio) its bottom part is pretty offset from an absolute black point of the space (see another gif)

After test printing with different combinations of Rendering intent settings, I found that "Perceptual" works well (no diff between with and without black point compensation). But I wanted to know if you folks can help me understand if this shape is normal and if not - what am I missing, how is it called and what can I do to make it look awesome?

Thx

[digitaldog]

The proof is the output*, but do consider uploading the profile somewhere where we can download and examine.
*You should always test output using good color reference images designed for that task. The color reference images RGB values are such that they are set for output and are editing and display agnostic. Test the output this way and examine for the same color issues so we know it's not your image-specific issues causing the problems:
http://www.digitaldog.net/files/2014PrinterTestFileFlat.tif.zip
This and other such documents can also be downloaded at http://www.digitaldog.net/

[soswow]

Thx for the reply. I'll take a look at test images you've linked. I've been using ones from https://www.northlight-images.co.uk/printer-test-images/ Usually printing

and

on the same A4 page. I believe they are pretty good for showing all the potential problems.

I've uploaded profiles here https://drive.google.com/drive/folders/1coIRYHqRlkJks6lfCDt_dpn6JYEyqDUF?usp=sharing
"ET-8550 ILFORD Omnijet - Photo Realistic Satin Paper - EPSG mt - v3 (white).icc" - the one made with ccProfile
"ILFORD-Semigloss-roll-2 agryl v3.icc" - made with argyll.

[digitaldog]

I viewed both in ColorThink Pro and didn't see anything alarming; Nowhere do I see "its bottom part is pretty flat." The ILFORD-Semigloss-roll-2 acryl v3 has a larger color gamut (Gamut volume) compared to the other profile: 623,032 vs. 552,379, and this difference is visible in the lower area of the gamut plot.
The number of color patches AND where in colorspace they are produced can make a difference in the resulting color gamut of any profile.

[Czornyj]

ColorMunki has no thermal drift compensation, so it's actually not such a good idea to scan hundreds of patches - all you're actually doing do is putting more and more thermal noise to characterisation data.

[soswow]

ColorMunki has no thermal drift compensation, so it's actually not such a good idea to scan hundreds of patches - all you're actually doing do is putting more and more thermal noise to characterisation data.

hm. Interesting. Not sure what it means though. So, are you saying the longer I keep the button pressed (and it reads the data into the buffer) the hotter the sensor gets, and so the bigger the inaccuracy due to the thermal effect is? If that is the case, does it matter how many of them I scan in one "go" (one column)? I still go through just an A4 length of distance no matter if it is 10 for ccStudio or 15 for argylle (or more)? If what you say is correct it's about how long I am going through each column and how much time I give it to cool down between each column. Right?
Is there a tool that can capture direct measurements from Colormunki? So I can experiment by measuring the same patch (not moving) over and over with long runs without pauses and then plot it with time as an axis. If what you say is correct I should see some change in the measured signal. I trust what you say. Just wanted to see it first-hand.
Also, if that is the case - it means my measurement will be dependant on room temperature? Which in my part of the world (Australia) changes a lot.

[soswow]

I viewed both in ColorThink Pro and didn't see anything alarming; Nowhere do I see "its bottom part is pretty flat." The ILFORD-Semigloss-roll-2 acryl v3 has a larger color gamut (Gamut volume) compared to the other profile: 623,032 vs. 552,379, and this difference is visible in the lower area of the gamut plot.
The number of color patches AND where in colorspace they are produced can make a difference in the resulting color gamut of any profile.

Thank you! I've looked at ColorThink Pro. Seems like an expensive piece of software that would only make sense buying if I work with that professionally. I was wondering if there are free/open-source alternative? If ColorThink Pro is a photoshop, is there a gimp version, basically?

So, the fact ColorSync Utility on mac shows the black end of the gamut shape is not at the crosshair is not a problem? (see attachment)

Do you folks know how argyllcms works? Is it something okay to ask here?
What I am thinking is - is there a way to iteratively improve the profile after the initial set of patches scan/profile creation? Does it have an option of intelligently recognising where the gaps are and what more patches to generate to improve an existing profile?

[soswow]

I've looked at ColorThink Pro. Seems like an expensive piece of software that would only make sense buying if I work with that professionally. I was wondering if there are free/open-source alternative? If ColorThink Pro is a photoshop, is there a gimp version, basically?

Seems like that question has been asked before, so googling is my friend. sorry for not checking first simple things.

[digitaldog]

http://www.colorwiki.com/wiki/Color_Management_Myths_26-28#Myth_26
Myth 26: Graphing profiles

[Lessbones]

http://www.colorwiki.com/wiki/Color_Management_Myths_26-28#Myth_26
Myth 26: Graphing profiles

good lord, that Powerbook G4 display-specific "myth 28" at the end of the page could use a heading update   

also completely OT, apologies, but Andrew, do you know where that "518,733 perceivable colors" number comes from?  The cube root of that number is 80.349 so I'm guessing somewhere else in the colorwiki it maybe mentions that humans stop perceiving differentiation in grayscale after that amount of steps is passed, but it seems like the truth would be way less linear than that...  Just seems like a strange value to throw out there without context.... I guess I could ask Steve...

[digitaldog]

Steve likely got 518,733 through a CTP color list, but yeah, ask him.
What is true is this device, like ALL devices do not provide 16 million colors.

[Kyle Jackson]

Thank you! I've looked at ColorThink Pro. Seems like an expensive piece of software that would only make sense buying if I work with that professionally. I was wondering if there are free/open-source alternative? If ColorThink Pro is a photoshop, is there a gimp version, basically?

Hi, if you're looking for something to view / compare profiles, I use Gamutvision. Their v1.4 is free (it's their legacy version).

Cheers

[soswow]

Hi, if you're looking for something to view / compare profiles, I use Gamutvision. Their v1.4 is free (it's their legacy version).

Thank you. Yeah, I've seen this one mentioned when googled, but it is windows only. I just tried installing/running it with Wineskin (on mac) but it doesn't start up =( Not an expert on this to debug it properly to know how to fix it.

[Kyle Jackson]

Whups! Sorry I missed the Mac reference..., I keep forgetting those are still a thing     I dunno if it can be run with Apples. I suppose if it's really needed, you can probably easily find an old Win laptop somewhere for like free and just use it to check ICC profiles.

[digitaldog]

I suppose if it's really needed, you can probably easily find an old Win laptop somewhere for like free and just use it to check ICC profiles.

The ColorSync utility (free on all Mac's) plots color gamuts in 3D.

[digitaldog]

So, the fact ColorSync Utility on mac shows the black end of the gamut shape is not at the crosshair is not a problem? (see attachment)

Correct.

[soswow]

The ColorSync utility (free on all Mac's) plots color gamuts in 3D.

Yeah, it does. You can even compare two gamuts. But I believe this a limited functionality. As in - you probably can't do much about except for reason about general shape and compare different ones.

Btw, I've made another set of patches, 372 this time on single biggish piece of paper. Resulting profile is in the same folder called "ILFORD-Semigloss-roll-3 agryl v4.icc" Its black point is even pointyier now :-D and because of that at least when comparing with prev. on using ColorSync mac app it shows it "smaller" (attachment) but I suspect they might have a different scale or something.

I've played with different intents+on/off black point compensation and RelCol + BPC works best.

I am still curious if there are ways of improving already made profile using feedback loop of some sort using Argyll.

[digitaldog]

Yeah, it does. You can even compare two gamuts. But I believe this a limited functionality. As in - you probably can't do much about except for reason about general shape and compare different ones.

What else do you expect a 3D gamut viewer to do?
At least in the case of CTP, it plots gamuts using the device->Lab (ie CMYK->Lab) "proofing" part of the profile.

[soswow]

What else do you expect a 3D gamut viewer to do?
At least in the case of CTP, it plots gamuts using the device->Lab (ie CMYK->Lab) "proofing" part of the profile.

I am noob at that. I don't know what to expect. I assume ColorThink Pro can do much more, I understand, for example.

[digitaldog]

Yes, CTP does a heck of a lot more than plot color gamuts.