Opacity in Photoshop Explained – and why you need to use it with Flow — The School of Photography – Courses, Tutorials & Books

Flow is like when you’re shading with a normal carbon pencil, lightly on a piece of paper. If you’re shading lightly this may be the equivalent of 20% flow and the mark making would be light grey. If you are pressing hard, so the pencil mark is instantly black, this would be the equivalent of a 100% Flow setting.

Flow in Photoshop gives you the ability to gradually build up to your darkest colour by overlapping multiple times in the same area without lifting the mouse click. A bit like shading back and forth with the pencil over the same area, gradually the mark would get darker. The more times you go over something with a low Flow setting, the more ink you are building up. Again, this is greatly beneficial when masking in Photoshop.

One thing to note here is that you will want to use a soft brush when using a low flow setting. Using a hard brush will give you a jagged edge as the ink flows out. Whereas, if you use a soft brush, the ink will blend together as it leaves the brush.