I'm looking to get my first system soon and was wondering about density. I am 20 years old with very diffuse thinning on top and you can actually see scalp easily now. I don't believe my back and sides were effected by hair loss that much if at all(knock on wood). I was thinking 80% density. I have uploaded pictures in various lighting. Please let me know if better pictures are needed, or if I should cut my hair then take pics, etc.

http://imageshack.com/a/img40/2395/7hyb.jpg
http://imageshack.com/a/img834/774/a0ds.png
http://imageshack.com/a/img855/6945/vn7c.jpg

A year ago with shorter hair:
http://imageshack.com/a/img32/9530/weo7.jpg
With flash:
http://imageshack.com/a/img690/6917/img0512kk.jpg
http://imageshack.com/a/img694/9096/img0507pw.jpg