Pointe blank

This is my favourite picture in the RCA's Degas and the Ballet exhibition. At 400 x 890mm 'Before the Ballet' (c.1890) is nearly anamorphic in proportion and the field of the empty floor falls away to a void. The real painting is blurry save for the feet of the dancers in the right foreground – the composition presses into the first girl's raised instep. The second dancer's exposed spine as she bends forward is reminiscent of Degas' many bathers, which Francis Bacon admired. You can see Bacon in the way in which the expanses and verticals of Degas' compositions are tensioned by the twisted human figures, and RB Kitaj in the renderings from photographic sources like a dry-brushed identikit.

Gustav Klimt would paint his figures nude and then proceed to cover them with clothes and patterning. Degas renders the dancers' upper bodies and the legs as solid forms but leaves the space between waist to knee as an impressionistic scribble. As sculptural plans his sketches for 'Little Dancer Aged Fourteen' are just plain odd: he plans the bronze in two halves and covers up the join with a real lace tutu. Beneath the fabric, the figure's right leg swells to join her stomach like a Henry Moore. The maquettes of nude adult dancers, modelled in wax as studio models and cast in bronze only after the painter's death, are fully detailed.

Many of the later, larger works that have been scaled up from photographs lose their dynamism but the hatchings and striations of his pastel drawings compensate for the magnification. 'Danseuses en bleu' still rocks. But nothing has quite the uncanny silence of 'Before the Ballet' or 'The Rehearsal.' Degas' paintings are sold as pretty, but like his 'Beach Scene' (1868) they are darker than that.

At their best the wide-framed little paintings are surreal arrangements of dead-eyed figures that play off each other but never interact. These rehearsals are have an ashen, spooky quality, from the staring dance masters to the unnatural poses of the girls. The longer you look at them, the more you realise something odd is going on.