The purpose is to bring out the essentials with as few lines as possible.
I think I have a different understanding at what a single line is. Take for example the fold at the side of their noses. To me a single line would mean, draw it in one swoop. Looking at your draft, you seemed to have raised and lowered your pen at least 4 times in such a short distance. That gives your lines a very insecure, scratchy appeal.
The proportions and angles of your lines seem to be on point, but that scratchy line quality really lowers the effect.
That's an amazing job on your facial lines and spaces and proportions, jan hackstrom.
My biggest suggestion for you is that most of the time, the lines seem or look like they have been executed with four shakes too many, thus resulting into a highly nervous look and feeling. You're caring too much about the drawing quality here. Would you please loosen up your dominant & non-dominant hands with 2 hours of 29 second quick expressions and mouth shapes to exercise them??? (7200 seconds/29 seconds/2 weeks, 248 poses/2 weeks=about 124 poses a week) (all holding your pens with your shoulders) As a result, your lines will give the bigger, fat swoopy look and feel in your outlines (contours) in one whole sitting.
Good luck, cheers, and I hope this've been helpful into your current and future goals. Practice makes progress, and progress makes myelin.
Thanks for the advice, Aunt Herbert and Polyvios Animations. Maybe I should work with the line. Usually I don’t care about artistic content. Finding the nature of the model is enough.
These are great! I can really tell you put a lot of thought and effort into each face. The proportions feel very accurate. The only suggestion I have is working on line consistency and making your strokes long and smooth rather than the short and harsh strokes you use here. Keep it up!