I'm using Photoshop with the Mix Brush tool to draw digital oil paintings.
The problem I have is that if you, for example, make the background black, select a dark blue color and then begin with your brush outside of the canvas (which naturally happens and is unavoidable), it "picks up" the apparently 100% white color that exists outside the black canvas, causing the paint to be way too bright. How do I tell Photoshop to treat areas outside of the canvas as "air" or "void"? (Or at least treat it as the same color as the canvas.)
I've asked many people and nobody has any idea. Looked through all the settings I could think of and I cannot figure this out. I was also told by a moderator that he was gonna re-post this after deletion (because of nonsensical replies), but that never happened, so I have to re-post it myself.
I even made a video showing exactly what I mean, so that nobody could possibly be confused about what I'm asking:https://streamable.com/s/3q061/edfrpz?autoplay=1