One of the most basic exercises in drawing is the sphere in light. The perfectly captured sphere shows an understanding of shadows, reflected light, curvature, and dimension in a single subject. In theory, once mastered, the same principles can be applied to replicating any three dimensional object.
As a digital artist with few skills in the traditional arts, I thought this exercise would be a good place to start learning how to use the tools. In my case, I wanted to gain a mastery of the skill of illustration, not a set of fancy pens / charcoal / marker.
For this sphere, I'm imagining the light coming from the upper right. The shadow should be narrow, since the light is coming from the top, but not as narrow as I have done it. The distortion in the shadow makes it seem like the ball isn't a perfect sphere. Also, I probably could've gone with some darker values with the shadow, since I'm using an ordinary Bic pen.
I want to use crosshatching to provide the shading. Cross hatching requires really good parallel lines, a skill that is clearly NOT demonstrated here, especially as the lightest shade value fades into the direct light.
Drawing circles is REALLY hard, apparently. The way I kept missing the circle gives this ball a cartoonish effect of movement, as the lines seem to indicate some kind of vibration.