>>1271516> I'll see if I can provide an example.Such as this one.
See, her skin still looks pretty dark, but now that I've lightened it from the originally edited version, it's a lot easier to make out the shading details.
(What I did was copy the darkened version as a layer and laid it over the original, then reduced the opacity of the darkened version by 20%.)
This isn't to say that you can't make them really dark like the ones I mentioned above, but the contrast of the 'lit' parts and the 'shadowed' parts of the skin is important. If you make the lit parts that dark, you have to make the shadowed parts even darker to get a similar contrast.