Face painting: difference between lighting and reflections.
When I'm painting human skin and portraits, I personally try to differentiate between the general lighting the face and the reflections that light causes on the skin.
A preliminar consideration: human skin is not completely matte but rather satiny in most cases. The sweat itself, oily skin and other factors mean that in most cases the light causes reflections on it. Not reflections as if it were metal, of course, but obvious.
This makes us to understand the concept of "reflections or shine" in our painting process within the general lighting process.
Differences between lighteen and reflections.
Personally, I always try to differentiate the two concepts. When I apply the lights in a portrait, wether it is overhead lighting, focal lighting or any other, my aim if to highlight the areas most exposed to light (normally the forehead, nose, cheekbones, chin...). This will gives is the look of depth and volume in the figure.
Once I complete this step, I decide in which areas to apply those highlights or reflections (it is not always necessary, it depends on the objective that we have set for the figure). Thus, they will be very specific points of light applied in the areas of maximum light (although not always) and normally using the color of the maximum light adding white. Therefore, It would be a matter of highlighting the areas of the skin where these shines would be caused with a color the has a large load of white color.
Depending on the general lighting of the figure, these highlights will be larger or smaller. For example, using focal lighting, the highlights will be larger and more visible than with general or overhead lighting.
I personally believe that this differentiation and applying final highlights gives the figures greater realism and strength in expression.
Red: lighting zone
Green: shine or reflections