You could try this Channel Mixer layer:
R 0, +100, 0, +23
G 0, +100, 0, 0
B 0, +100, 0, -10
If that's not satisfactory as a quick fix, then it'll have to be patient cloning.
Hi @pennylacy, sadly the instructions that come with the X-Rite are feeble.
Follow my step-by-step directions here: https://www.damiensymonds.net/calibration-instructions/
And save them as 16-bit TIFFs or PSDs, yes.
Are you sure you even need to? Remember, "merging to HDR" is only for people who don't know how to edit raw files; or for cases where one raw file genuinely doesn't capture the entire tonal range.
I know you're not the former, so is the latter true?
Of course there will be Levels work to do in Photoshop afterwards, just like any other photo. But you MUST NOT skip the raw editing part of the workflow. That's madness.
You're supposed to do the raw processing first.
Then (I think) save as 16-bit TIFFs to put through Photomatix. And export as another 16-bit TIFF out the other end.
As long as their printing is accurate, this will look beautiful on canvas.
But you're right to be cautious - if their print profile is even a little bit wayward at the highlight end, it could quickly lose its impact.
Hi @Tatiana, I hope you don't mind me making a post here. I can't access Facebook at the moment.
The reason your colours change so drastically is that you're assigning, not converting, to sRGB. Never assign.
However, it might not be as simple as converting either. Follow this troubleshooter.