Updated: Jun 11, 2018
Sketching with a pen or pencil has always been one of my favorite ways to produce art. Not to mention, it doesn't cost anything to sketch. I find that I will use a regular black ball point pen and sketch something that appeals to me.
Pens can add more depth to a picture mainly because of the ink. Adding depth is as simple as going over one spot until it is dark enough to help the object to stand out. In this image I sketched of my daughter picking up a snow ball, doesn't have a lot of depth and she almost blends in with the background, somewhat creating an illusion to the whole picture.
This is one of my favorite sketches with pen. There is not a whole lot to it, but the boat, which I have highlighted to be the "main feature" stands out just enough. The second "pop" is the light house, which I wanted to somewhat blend in with the background.
This is a great way to add the depth to your sketch. If you take a look at the image above, you can see I added "shadows" to the oars by cross-hatching. I used a .005 micron black pen to add a light depth to it. Inside the boat I used a .08, which helped the boat seem more 3D.