Technical note: this was not done with a telescopic lens. It was shot with a 50mm lens on a slow film (100 iso) then scanned to high res, blown up and cropped. Hence the detail.
A rear view of a vivacious model named Stella, who forgave me for the emphasis I was obliged to give to her arse due to the position of my easel in a crowded room.
Going through some old paperwork I found a CD of pictures and this is one of them. It was taken a few years ago on Hampstead Heath. As I recall I didn't have time to get an eye to the viewfinder, and took the shot literally from the hip.
A different approach: the paper is rubbed with a light coat of charcoal. The drawing is done with an eraser and highlights added with chalk.
Model Sophia.