OK, it looks like it’s probably only me having this issue - I searched on the Internet, haven’t seen anyone else asking about this. I hope ZbrushCentral can give me some help.
The problem I have is, when ZBrush is on its Full Screen Mode, the See-through function stops working. Whether it’s 4R7 or 4R8 or now ZBrush 2018, it never worked. I mean, the opacity of the canvas is always 100% regardless what numbers are on the See-through slider. The only way I can actually use See-through as a tool for the reference images is to manually enlarge my screen instead of using Full Screen Mode. But enlarging screen this way sometimes causes another problem that makes me not be able to hit on the right buttons I want to click, because the cursor seems to be off somehow with the non-full-screen-mode. To avoid this, I basically just have to totally give up the See-through feature.
I’m running ZBrush on Macbook Pro with Cintiq 27HD, system macOS High Sierra - probably this is why this is happening. Not sure if it can get fixed? Or did I miss anything here?