Charcoal

Sometimes 20/20 vision is not helpful. When we observe whatever we are drawing there is a ton of information going in through the eye gate. And an image filled with needless details cripples the effect of a piece. The goal is to edit and simplify.

Squinting our eyes just enough simplifies values and over all helps us to see a simplified version of what we are looking at. Squinting also helps you to see simple shapes very clearly. Nailing those simple shapes helps with the overall essence of the piece.
source