The greeting photograph at the latest exhibition at Timothy Taylor’s main space in Carlos Place by Diane Arbus, one of the best-known and most discussed American portrait photographers, shows a small girl in a nightie, at dusk in an empty field. It sets an uneasy tone. As with Arbus’s “freaks”, there is a suggestion of domestic chaos. Yet like those sullen strippers, Russian midgets, “Identical Twins”, the girl poses eye-to-eye with Arbus, a mark of trust on both sides of the camera.

The anonymity and strangeness of these pictures contributed to accusations of voyeurism — but the joyful subjects at the second, more interesting exhibition at Timothy Taylor’s smaller Dering Street space, invite you to see Arbus’s work afresh.

These 13 portraits were shot in the months before Arbus’s suicide in 1971 at a home for people with mental disabilities, mostly Down’s syndrome. Two Downs women, linking arms and grinning through clown masks, set the scene and raise the question of why Arbus spent her last months here. For her, you sense, they humanised a then taboo section of the population. Visiting during fancy dress parties and Halloween, Arbus reveals playfulness, physicality and a capacity for happiness epitomised by the girl lying on grass. In hats and clown outfits, they dance unselfconsciously — exuding the joy which the photographer presumably craved.

Diane Arbus: until 27 June (020 740 93344, www.timothytaylorgallery.com)