Using New Lines

After our seminar about line quality I've been trying to encourage myself to use my sophisticated line qualities and generally just give more consideration to what kind of lines I'm using and where. I chose to use the motif of some wrestlers faces in all my line drawings as I think they're quite interesting and enjoy experimenting with the colours and features of each different character. 

These two were some of my favourite outcomes. I used some thick graphite and quick, hard lines in conjunction with soft shading for detail. This was both quick and effective to do which is a mega bonus. However, I'm not quite sure how you would go about adding colour to this, maybe this is something that could be done on photoshop?