I think the contrasts are good, I know when I do darker skin tones it is something I find hard - I sort of get shadows and highlights and not much left in between to make a face. That looks good though and you were able to build up some nice skin tones!
I like the hatching here! Gives the skin a nice texture.
I think you might have concentrated a bit too much on trying to show all the subtle curves on the shape of the face - they seem a little exaggerated. If you're going more for realism, try thinking of it like this: the majority of the shape of the face is given by the skull. That means straight, solid lines when you#re constructing, except on fatty/muscle areas like the cheeks. Playing straight lines against curves gives a strong effect for describing which parts have bone underneath and which have fat/muscle.
Watch your colours on the eyebrows as well - one's brown where the other is bluish! (not that it really stands out, it's just something I picked up on close observation )
I seriously love this image of yours! Already faved it actually. You are really good at lightning and shading. But most of all I like you make the face so complex against the very easy done hair. It makes it so interesting to look at. Love it! Well done!
I really like your use of cross-hatches to define the contours of his face. I see this technique frequently with ink, but rarely with digital media. The shading and shadows of the face are very well done; I especially appreciate how you used different colors, sometimes light over dark and sometimes dark over light, to create your intended shade.
You might consider adding a touch of dark to mid-range purplish-brown of the lower lip to the upper lip for some highlights. That would tie them together a bit better; as they are they don't quite seem to match. You also might consider adding just a little purple to the shadows under the cheekbones and eyebrows to tie the picture together even more.
The fact that you added a lot of detail to the face then faded the rest of the picture out, is perfectly fine and helps to focus your viewers eyes. However, you could add a little more detail to the hair. There's no need to go to the depth you used for the face, but at least give it a few lighter and darker areas so that it matches the details of the chest area.
Over all, this piece is very well done and your style adds a lot of interest to what could have been a typical portrait. Nice work!
First of all I absolutely love the way you did the skin of face and neck. Your hatching technique renders lighting perfectly, the contrasts and tones are wonderful. It's especially impressive looking at the reference picture, where the lighting wasn't as strong. You made the whole face more luminous. I find it ok that the shoulders and chest are less detailed, it really brings the focus to the face.
As for what could be improved, the lower half of his face is great, however I think the upper half is a bit too narrow. His forehead would need to be broader and his eyes a bit more distanced. I think the eyes would benefit from having a bit more light in them too. Also, the color of his hair is kind of flat. It would be nice if you had added a bit of hatching there too. Finally, his shoulders are a bit narrow and female looking, they should be broader.