Jeff Lait

Checking the code, we aren't binding Alpha :< So the alpha attribute is not supported. I've submitted an RFE (152678)

The attributes are probably most similar to "primitive" attributes, but Copernicus has one-wire-per-primitive so they also look like detail attributes.

They are for whatever extra non-image meta data you may need to attach. USD in particular uses them to store the output file name to ensure things are saved in the proper location.

The File COP will also fill out all the extra data from .exr here, so you can get stuff like cryptomatte manifests, etc, in it.

Having a wrangle to update them does seem like a good idea.

Thank you for the detailed assessment. Trying to put a fixed size logo on top of a plate is something that should be easy, and isn't.

I'm going have to look into crop's size_ref, I had imagined setting units to Pixels would have done what you wanted, but it seems not!