here is a problem that's been bugging me for a long time and as I didn't find any solution from the web, I thought it may be time to ask for help.
When I export a .psd from my 3D app with a layer of objects rendered as plain red, green and blue colours to use as masks from RGB channels I run into edges problems.
When I copy/paste (or copy merge/paste) the channels into layers and blend them with Lighten, Linear Dodge or anything else I always have visible edges, like pictured here.
This lead to nasty edges in the final image :
I also have the same problem when I invert the masks.
This happens in Photoshop CC 19.1.2 on OSX 10.13.3 in a 16 bit RGB file, but I had the same problem on earlier Photoshop versions and other image modes.
Maybe this is a normal behaviour but I don't feel like it, so if anybody is willing to shed some light onto the problem, thanks!