Hi there!
I have a series of pictures taken with a R5 and CR3 files, of some items and included the ColorChecker Passport classic 24 natural object, chromatic, primary and gray scale colors in some pictures. Used Neutral 8 for the white balance (on a iDisplay Pro calibrated monitor) and ART.
The colors are pretty close. But I want them to be closer. But I cannot see how I can do that. Any ideas?
Thanks in advance!
Iām guessing by ācloseā, you mean āclose to the original ColorChecker when I hold it up to the screen displaying this imageā. Well, you can use that ColorChecker to make a R5 camera profile, then use that profile as the input profile in your raw processing. And hope you did it better than, or have a better ColorChecker than, the person who used their ColorChecker to make the profile in ART. 
Seriously, if youāre going to do reproduction work where matching the colors of a subject is important, youāll want to learn to make such profiles. Also the ColorChecker neutral patches are useful in determining a white balance specific to the scene.
Hi,
Iām far from an expert, so take this with a fistful of salt, but if you want accurate colours under the illuminant you used in your pictures, you would need to have spectral data for the colorchecker patches, with which you could create an appropriate icc (or DCP) input profile. ART ships with a dual illuminant profile taken under d65 and tungsten light, but Iām not sure that it is of the highest quality ā itās generated from the dpreview studio scene, I think itās decent enough for general-purpose use but probably not for reproduction work
HTH
Thank you for your response Glenn.
Well the sRGB, CIE Lab and hue/chroma values of the ColorChecker are known. In sRGB Neutral 8 is 200 200 200. Dark skin is 115 82 68ā¦ so each of the 24 values are known. When I hover, check, using the color picker button I would like to see (about) the same values. As the array seems to be around for many years I was wondering if there is a method to do that.
Grazzie Alberto.
I see here āCIE LAB values use illuminant D50 2 degree observer sRGB values for illuminate D65ā.
White balance off a grey patch and use exposure with white grey and black patches to set the tones correctly. then use the vectorscope and crop to the primary color rowā¦then rotate these hues with the hsv equalizer toolā¦either to the hue they are supposed to be by spec or just align with the primary nodesā¦this should make the colors close and pleasingā¦of course you color profiles and monitor calibration would need to be set to view properly and I am not sure where art gets the picker values fromā¦in DT it comes from the histogram profile color spaceā¦not sure in ART??
@Henk could you post one of your raw filesā¦some time back when I tried one of the first builds to support CR# in DT. I tried to use the color calibration colorchecker feature on an R5 or R6 cr3 and I could not get it to improve too muchā¦other raw files including a couple of cr2 files seemed to get better improvementsā¦might be nice to revisit this with one of your color checker shots if you can share it ā¦
Thank you Todd!
Puzzling what you meant by āthe vectorscope and crop to the primary color rowā¦then rotate these hues with the hsv equalizer toolāā¦ Will have to find those tools then!
The monitor, although calibrated, was not my worry. It was more the basic question if one could achieve this.
This file is from the same set but slightly more interestingā¦
IMG_20210901_4396_R5.CR3 (47.2 MB)
Process a bit like this ā¦ and emulate the process with scopes in ART
Around 5 min you will see the bit about cropping to the primariesā¦
Again this is video but you could do similar things with the scopes in ART to tweak tone and colorā¦Gerald make nice videosā¦
Mr Undoneā¦ yes!
Nice info! Thanks!
Not sure if it is a manageable task but I wonder if it would be possible integrate the DT code that creates optimized channel mixer settings to give a closer match to a colorchecker. I know that you have ported some DT code in the pastā¦It would be a nice addition but not being a programmer I have no idea the scope of the task from not too hard to impossibleā¦just thought I would ask?? As always thanks for your massive contribution with ART.
Porting the code shouldnāt be hard (though I havenāt checked), but Iām not sure what benefit this is supposed to bring ā in order to assess that I would need to understand how this works first, which is not clear to me at the moment ā Iām very far from an expert in colour management.
Thanks for your reply ā¦in DTā¦explained here.
I am also not an expert but basically in ART the user would select a color profile or DCP file and then after that in the pipeline the DT code would analyse the colorchecker in the image and derive a set of channel mixer settings/coefficients to make the colors more accurateā¦in many cases in my testing my test shot might have a delta E of 7 or higher for the average which is not great and the routine in CC of DT can often reduce that significantly to something under 3 so much betterā¦
Maybe Iām missing something (quite possible), but I canāt see anything that couldnāt be done with dcamprof alreadyā¦
This is integrated so no need for tiff files or scanning in and running dcamprof command lines and then copying the icc file back for use with ARTā¦.also it works with the existing camera profile and the selected wb setting and then just optimizes itā¦.basically takes only a few clicks and its doneā¦.
