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That's the difference in my opinion between a sketch and a drawing ; when I do a sketch I keep that rough aspect that the scratchs give, and not necessarly trying to made a realistic texture. But when I do a drawing portrait, which takes me hours to do, I want a hyperealistic result, and so in that case I blur my lines to get a photorealistic result. But you can also get a really realistic result with a single ballpoint pen, although the BIC does leave traces, which is very impressive!