I've been sketching thumbnails using the brush tool, only in one color (black) with varying levels of opacity for shading. I had line art on one layer and shading on another, but accidentally shaded over the line art and can no longer undo/step back. I need to erase/remove the shading and keep the black line art intact, but PS doesn't seem to be able to differentiate between the varying opacity levels and treats it all as a single color when I attempt to use any of the special erasing fuctions like magic eraser no matter how high I set the tolerance or the selection tools, etc. It's a simple sketch and I could draw it again, but I'm very rusty with PS and I'd like to know if there's a solution in case I run into this again. Exibit A below. Suggestions?
