one image with 2 alpha channels. Can I choose which one to use

#1

Can I tell nuke which alpha channel to use if I have imported a rgba.psd with two alphas?

Is it normal to work with images that have multiple Alphas? or multiple channels in one image?

Thanks in advance.

#2

Yes, Nuke is designed to handle an arbitrary number of channels. I am not sure how it works under the hood, but I would guess that if the channels aren’t tagged, or if they’re Alpha1 and Alpha2, as Photoshop likes to do, that Nuke will treat the first as alpha and the second as a z-buffer. You can use the Shuffle node to change which channel is used as the alpha and rename the other to whatever you need, or even break it out into a separate branch if you want to.

It’s not uncommon to see EXR files with many channels. They might carry motion vectors, lighting passes, z-depth, normals, and so on. You can also store many channels in a TIFF, but handling of those extra channels is not as standardized.