Nathan Lorenzana showing off his insane skills with a ballpoint pen portrait.

Mesmerizing as usual.

Check out his sketchbooks from 2007, 2011 and 2013.

Scott Robertson talks about how you can use line weight to give your drawings more impact.

The topics covered are like when to use thick and thin lines, how to differentiate foreground and background elements. It's applicable for objects and landscape subjects.

Almost 1 hour of video featuring John Park's sketchbooks