I've been using Paint Tool SAI for all my digital work up until now where I've switched to Photoshop cs6. I've come across this problem where the brush stroke becomes darker when it travels over another brush stroke regardless of pen pressure (the dark square in the middle of the cross). I found this goes away if I turn the opacity up to 100%, but I don't want the opacity to be at that level while I'm painting. How do I make this go away or is it just down to opacity and will always do this if opacity is lowered? Thank you!