It is hard to beat the simple elegance of a black and white portrait. More cost effective than a colour picture, and very focussed.

Biro portraits give higher contrast than pencil and they provide sharper details so smaller sizes are feasible (as opposed to pastel pictures). Gradients aren't as smooth as pastel, even using pencil, but the precision of the details allows for more complex compositions. This makes black and white a good choice for pictures with multiple subjects, such as family portraits. Pencil can provide greater smoothness than biro, but is interrupted by the grain of the paper (which biro ignores). Biro pictures create their own impression of texture from the variation in pen strokes.

Recommended sizes are A4 and A3.