spectrophotometer: I want to measure my colorchecker

Hardware
1

Hi everyone,

I’d like to have some fresh spectral data on several Gretag-MacBeth charts for use with dcamprof (in order to build .dcp profiles, ref: how to create a dcp for an artificial light source)

  1. X-Rite Colorchecker Passport (page 1 and page 2), after 2014 — mine is a 2019 edition.
  2. SpyderCheckr24 — not sure if there are changes in dyes in their recent history
  3. possibly other charts, like the brandnew Spyder Checker Photo, or some other custom chart I’d have printed.

I understand I need to look for (someone with) a spectrophotometer (as I can’t necessarily justify the expense of acquiring one).

But then, to narrow that search down, I figure I need to pay attention to what I’m measuring and the possible outputs (CGATS, txt, …, you name it). So, factoring in the Colorchecker Passport with rather small patches, a device such as the Colormunki Design is not the right tool for the job.

How would you go about that?
(Or I could use ready-made files, if I actually found them, i.e. something more recent that what’s bundled with @gwgill’s awesome argyllcms: ColorCheckerPassport.cie was created back in 2012, so before the dye change in Nov. 2014.)
Thanks for your input!

2

Now, dcamprof comes with both old and new ColorChecker reference files; any problem trusting them?

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3

Salut, @nonophuran!

Colorchecker Passport … small patches, a device such as the Colormunki Design is not the right tool for the job.

??? How small are your patches? Mine can be read; here is a swift proof:

Screenshot 2023-06-05 103759

Have fun!
Claes à Lund, La Suède

4

(i) dcamprof comes indeed with old and new references files, but it’s just the half passport, i.e. the 24-patch card. It’s not taking into account page 1 18-patch card (for WB temperature adjustment, and the additional gray scale).
Reference directory from github: dcamprof/data-examples at master · Beep6581/dcamprof · GitHub

(ii) argyllcms has a ref directory, which does contain a .cie spectral data file for the pre-2014 colorchecker passport, with both pages.
Ref: (not the official repo, not sure if there’s one, outside of Mr. Gill’s website) ArgyllCMS/ref/ColorCheckerPassport.cie at master · capnm/ArgyllCMS · GitHub

(iii) the luminous landscape forum has some data, for a pre-2014 colorchecker passport, too:
page 1 : DCamProf - a new camera profiling tool
page 2 (24-patch card) : DCamProf - a new camera profiling tool

Well, Torger was explicitly mentioning this in the dcamprof documentation:

Note that some targets may have too small patches to be read successfully with your instrument. For example an X-Rite ColorChecker Passport cannot be read by an X-Rite Colormunki spectrometer.

Ref: https://torger.se/anders/dcamprof.html#target_ref manual page.
Mine is a 2019 X-Rite Colorchecker Passport 2. Are there several models for the colormunki out there? I assume Mr. Torger was talking about the Colormunki Design, but I have no idea.

5

Oh yes, there were several models of the Colormunki. colormunki at DuckDuckGo

Mine is a Colormunki Photo.

6

OK, lucky me (?), I now have a second-hand EFI ES-2000 (more or less a “rebadged” version of i1pro 2).

If you have a shortcut so I can do my measurements in argyllcms, I’m all ears!

(I hope you’ve had a nice summer so far)

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7

Quick reply to myself:

# using Argyllcms "chartread"
# - input: ColorCheckerPassport.ti2 file
# - output: ColorCheckerPassport.ti3
chartread -v -c 1 -l -p -A A -H -S -P ColorCheckerPassport

TODO:

  • figure what further conversions are required, for use with dcamprof
  • refine the procedure drafted several times in the thread :thread: how to create a dcp for an artificial light source
  • take measurements again (5 times and then take the average or the median values ?) and provide them to the community (argyllcms, dcamprof, …)

thanks to @gwgill for the kind help given via email, on the argyllcms list.
ColorCheckerPassport.ti2.txt (2.8 KB)

Sample result (one pass):
ColorCheckerPassport.ti3.txt (45.6 KB)

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remember that spectrophotometers with incandescent / halogen bulb light source ( so for x-rite/gmb that means everything befor i1Pro3 which has LED source ) are subject to tungsten vapor drift … it may or may not be noticeable based on your target/patches

“At its worst, I was seeing errors of 2.0 Delta E between cold and hot!” wrote the author of ArgyllCMS himself once :smile:

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