Best/easy way to get from grayscale to color

[Takiro]

Hello fellow artists. I’m painting digitally for years now and for some time now my workflow is that I start with a grayscale image first, and add colors later. Over the years I tried many approaches some worked
better than others some worse but none were really satisfying.

Usually a grayscale image looks like this when done

This is of course just a 3D render but after my first step this is pretty much how it would look like when painted too. As you can see everything is shaded as it would be a plain white object, there are no values of the local colors yet, no reflections, no highlights (sometimes not even all the shadows). I do it that way because I have a hard time figuring out shading when there is already color, my eye seems not able to see value differences when there is color involved at the shading stage. so that’s why I do this first.

Years ago I would do an intermediate step to add the just the values of the local colors, at this point. I don’t do it anymore now but for completeness I add it here.

This was usually the part where I also gave things materials like when things shine or reflect a lot. Nowadays I skip it completely because of the fact that I most of the time, decide for the colors of things as I go and that I am very bad at guessing what colors have which values.

When doing this second step, adding color was of course pretty easy because then I only had to ad a color layer set to Color blending mode. But as mentioned I’m very bad ad guessing the value of colors so I usually was (negatively) surprised by the outcome and hat to do so much adjustment I basically had to repaint everything.

So know I go to step 3 directly, the coloring. I take the grayscale image from step one and use layer blending modes to get the color on top (or behind) basically using the grayscale image (since it as no values for local colors) as a pure shadow/light map. Since I still need the value of the colors I pick, Color blending mode is not an option as it would in step 2. I tried other blending modes and the results are okayish but I still feel there is maybe a better way.

So my question is basically, is there a good way to get from step 1 to this:

Currently I add a layer on top of the grayscale and set it to Hard Light or Overlay and paint with the colors on that to keep both the colors and the values. This is also the stage where I add/remove highlights and stuff. I don’t expect a perfect result like my examples I did with Blender just your input on how to work quicker or more correct with less fixing afterwards.

Looking forward to hearing your input on this.

[hulmanen]

If you really want to just essentially do a lighting pass and colour that, then you could paint your colours on a later set to “multiply”. This would mimic the way lighting passes would be composited with diffuse colour. Note that reflections and highlights would need to be done separately.

I wonder though, why not have the grayscale painting contain the values you want? The values you use are usually much more important to the final result than the colours. So if I was to do a grayscale version first, I’d make sure it represented the values of the finished painting as well as possible. After that, a layer set to “colour” mode should get you there. I don’t really like to work that way though, as I find getting the to the tonal variations that one likes to see is more work than just painting in colour directly.

[hulmanen]

@Takiro sorry, I was a bit harried and seem to have skimmed your question a bit too much, you did say why you want to paint just the light contribution, not the materials and light combined. I don’t know how much work you’ve put into the issue, but generally I think learning to see the values of your painting by doing a lot of grayscale value studies is so fundamental that I really would recommend just biting the bullet and working on that, if at all possible.

Maybe that just doesn’t work for you, I can’t say, but then painting colours in multiply and doing a highlights pass over that would be about what I can come up with. But I don’t really see how your workflow mitigates how hard it is to judge local value - aren’t you just postponing that decision until the coloring phase?

[Takiro]

Yes that’s true I postpone it until the coloring phase. This has the ultimate advantage that I can decide for actual color’s much later in an artwork. Basically right before the rendering phase.

I mostly want to know if there is a combination of blending modes that more accurately let me paint over with color and combine the values of the current color with that of the grayscale painting I already did.

As I wrote, using a Overlay or Hard Light layer over the grayscale image already gives good results as it keeps the hue and value and combines this with the values on the grayscale layer. But maybe there is an even better solution because Overlay for example does look weird on very bright areas, like overexposed.