Painting with additive opacity

#1

I asked this in Photoshop forum, but I thought I’ll try here also. I realized that I always needed a setting that I can’t produce.

Basically what I need is that when I paint a 20% opacity stroke over a 10% opacity stroke, I would get a 20% opacity stroke, not a 30%. And when I paint a 10% opacity over 20%, I still have 20%. So the opacity rises only if the painting opacity is higher to the one already painted, and colour changes accordingly to opacity/pressure. Image below should describe it more:

It’s for sure possible to achieve. Does anyone know how to do it in Painter, or any other application? Any help greatly appreciated.

#2

Have you tried different brushes and settings? I think it’s possible, but you have to know what to tweak. I think if you set Resaturation to be controlled by pen pressure, and then set Opacity control to none, and set bleed to zero, you might be able to get that behavior. I tried it and it works, except for some reason I can’t get Resaturation to be controlled effectively by pen pressure right now (I suspect it’s a problem with my tablet at the moment). Try it and see if it works for you. Oh, and I just used the most simple round brush.

#3

Rob’s Basic from Rob’s Brushes is a brush that is set up similar.

It partially works, but only on white background, and it makes it unusable for me. I need the opacity to be controlled by pen pressure, so that I can paint under it later.

But nice try :stuck_out_tongue:

#4

The only reason why my Basic Round brush works (partially) is because of the Bleed. It’s actually smudging the background onto the previous brushstroke. It’s not exactly what you need, and in some cases might screw things up, such as dragging unwanted colors into the previous brushstroke. If there was way to map the Resaturation levels to hotkeys like with the Opacity levels, that would actually do the trick, except you’d have to hit a hot key to get the value you want each time you lay down a stroke.

#5

I actually found your own brush set, and didn’t know it. :slight_smile:
Big thanks for making it.

I’m really surprised that Photoshop can’t do what I’m after. If colour is a number (or a couple of numbers), and opacity is another number, then it’s a simple calculation - set pixels colour according to pressure, and set pixels opacity according to pressure, but only when it gets higher that the opacity that pixel already has.

Maybe it’s possible to make a plugin that can do it.

#6

Digital Watercolor variants (e.g. Broad Water) can do this. If you’re on a layer, it must be Gel because the edges of DWC are white.

You may want to set the Fringe to 0 to achieve the exact look you are going for.

Phil

#7

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