- Add Cryptomatte layer into the render elements (see "cryptomatte save" image)
- Render, then save to CXR (same image as above)
- Rename CXR to EXR
- Open in Photoshop with EXRIO (see "tom exrio settings" image )
- Hide all layers to leave just the desired mask
- Select All and Copy (see "cryptomatte select all copy" image)
- Remove the Select
- Re-enable the RGB layer, and add a layer mask
- Alt click on the layer mask to enter editing mode of the mask (
https://studioratonline.com/blog/paste-into-layer-mask-photoshop/ )
- Paste the copied cryptomatte mask into the layer mask
- Alt click the layer mask to return to viewing the layer and not the mask, and now you have that individual object masked out (see "cryptomatte alt click mask and paste" image)
Repeat by duplicating the Beauty RGB and adding a mask for other objects you want to process separately (or layers, etc. - there is no by materials option yet), and of course layer those onto a Beauty with no mask (haven't set that up in the screen grabs). Apply adjustment layers to the masked-out layers so you can adjust them as needed, e.g. change their color.
Or can do this not for the Beauty layer but for Reflection, Refraction, Direct, etc. if you have added those, e.g. to control the reflections in a mirror separately from the other objects. Note that other masks can do this particular example and likely more easily; cryptomatte really only offers benefits when using things like DOF or Motion Blur, where the masking is better with Cryptomatte as it accounts accurately for the "soft edges" in the blurring.
Also note tone mapping will have to be done in post and is best left at defaults in the render.