Think about the focal point and use contrast, positioning and size to draw attention to it. Use pencil very lightly when you start to sketch out your composition so any mistakes can be rubbed out.

The same rules about texture apply to drawings and paintings ... They are good for showing contrast. If you only have one type of pencil, you could also use wax crayons or felt tips.

These sensors pick up changes in pixel contrast, outputting a positive or negative number based on the direction the pencil is beginning to fall. An NXP2103 running at 64 MHz reads in the values ...