Color Calibration - Data update for Spyder Colorchekr photo.....

As a result of a recent conversation on pixls.us I have discovered a couple of issues with the data used in the colorchecker.h file that supplies values for the patches used in the calibration functions of the color calibration module.

The first one is that we have entries for 2 versions of the Spyder cards from Data Color, ie a pre and post 2018 version of the cards for the 24 and 48 patch cards. From what I have been able to find there has never been a version change published by datacolor and I am not sure why this was included unless it was believed to be similar to the x-rite cards which did have a change.

Indeed the values in the colorchecker.h file which uses LAB values are the same for all 4 entries so I believe there should only be a single entry for each and no versions..

DataColor only provides as far as I have been able to find a pdf for the colorchekr 48 and states that the 24 is just the right half of the checker so use the same values. This has been the same data since the cards first came out around 2014 I believe.
https://www.datacolor.com/spyder/downloads/SpyderCheckr_Color_Data_V2.pdf

However the more recent Spydercheckr Photo, which is a newer more compact version of the color checker 48 does ues different data. This card maintains the same layout as the colorcheckr 48 but uses new ink/pigments that it touts as ultra flat and uses a new paper. This is clearly mentioned on the website.

The product and this new element of the card is described here...

https://www.datacolor.com/spyder/products/spyder-checkr-photo-sck310/

There is no update or other data provided for the card...

Having explored Argyll and Lumariver to see what data they used I thought I would check the actual software that comes with the Spyder cards... In a subdirectory of the software I found its reference data file...a plain txt file.

SpyderCheckr Default Measurements.txt

As you can see it has 2 sets of data. One for the 48 ( 1/2 used for the 24 version) and at the bottom a second set of data for the spydercheckr photo's 48 patches.

The data are consistent with the Datacolor pdf above and what we use in DT for the 48 and 24 patch cards, however in DT we also use that same data meant for the 48 and 24 patch cars for the newer photo released in 2022 and it should be ussing that second set of data taken from the Spyder calibration software..

The values from that software are read across the rows of the open card so that would need to be correctly parsed to match DT which orders them down the columns...

In summary we could have a single entry for Spydercheckr 24 and 48 to clean up the dropdown list. Since the same data is currently being used there is no need for this but it would make the menu simpler. If someone has evidence and data for a change in 2018 that should be validated and that should be added. More importantly the LAB values in colorchecker.h for the Spydercheckr photo version of the card should be updated to reflect those included and used by the Datacolor software as specified in the Default measurements file attached above... Currently we are using the same data for it as for the 24 and 48 patch variants of the card...

The colorchecker.h file that contains the data is pretty simple and this change would be merely an update of the LAB values for that card... I will parse and prepare a version with the correct data.

Point of question do we also modify it to remove the extra versions of the spyderchekr cards ie the pre/post 2018 declaration??

Start with colorchecker.h and compare the SpyderCheckr entries against the attached SpyderCheckr Default Measurements.txt and Datacolor PDF. Verify the row-to-column patch ordering, then update the SpyderCheckr Photo LAB values and determine whether the pre/post-2018 entries should be consolidated. Done means the calibration data matches the documented card variants and the dropdown entries are justified.