The Whitechapel Gallery’s scan of photography from the Indian subcontinent is enormous. One hundred and fifty years, three countries, several hundred works (from the documentary tradition, the private, the commercial, from contemporary-art … ). Poor photography, still the last medium in which such sweeping gestures are considered to make any sense. The result of the ambition of this show is that it has to skate almost trivially over vast acreages of great interest. It makes a wonderful invitation to seek more detail, but it provides little detail itself.

The impulse for the exhibition is both laudable and negative. The very rich presence (both past and present) of photography in south Asia has many aspects which do not fit into patterns dictated by the history of photography as written in Europe and the United States. So this exhibition, unlike many earlier, seeks to show only works by photographers from the region and to allow their expressions of cultural values to be heard in their own context. This is worthy enough, but it is lopsided. From the earliest days of photography in the mid-19th century, its development on the subcontinent was influenced by developments in Europe. To try to look the other way is perhaps a necessary shove to a pendulum which has been stuck on the Eurocentric side for too long, but it is an adversarial position and not a neutral scholarly one.Spread over two floors of the large gallery space, the show looks oddly drab on the lower floor and much more lively above. It is arranged thematically and not by date, and the curators follow five threads (the portrait, performance, the family, the street, and the body politic). These are more or less arbitrary, and they intersect often.

The grouping allows for lively comparisons, and provides a minimum of necessary guidance to European viewers in a maze of mostly new names and stories. But the stories, in truth, are better told in the book which accompanies the exhibition. On the walls are lots of pictures with minimal context, a kaleidoscope of snippets.

It is full of fascinating and lovely things. Here is a doorkeeper from the 1880s by the great Lala Deen Dayal, tiny against his massive studded door, with the sweep of shadow across the great door matched by the sweep of his dark cloak across his belly. Here is an exciting construction from 2007 by Rashid Rana in which the repeating pattern of the surface treatment of the twin towers in New York is made of thousands of little views of street-scenes in Lahore – Rana’s point being that the great shining vertical cities are often made by the labour of those who live in the sprawling dusty horizontal ones.

Here, too, is Umrao Singh Sher-Gil prancing about in his underpants on a bed in Paris looking like the villainous fakir in the “Tintin” books. Far from being a comic figure, however, Sher-Gil is of great importance in the story of Indian photography. Born to an aristocratic Punjabi family in 1870, he was a linguist and classical scholar as well as an enthusiast for craft skills like carpentry and calligraphy. He married a Hungarian opera singer and spent a large proportion of the 1920s and 1930s in Budapest and Paris, from where he brought back all that was newest in photography. But he had been an enthusiast for years: his early pictures date from the late 1880s, and he was perhaps among the very first in India to adopt the autochrome process of the Lumière brothers.

Umrao Sher-Gil was the father of the painter Amrita Sher-Gil (who died young in the 1940s) and the grandfather of the contemporary artist Vivan Sundaram. Both of these have a part to play in this exhibition, where Sundaram reworks his grandfather’s pictures by a form of computerised collage which is both a tender dip in the family archive and a more acerbic contemplation of the various parts taken by photography as catalyst or protagonist in personal identification.

The exhibition is full of links of this kind. A pleasing one is in the simple portrait by S.B. Syed from the 1850s of a woman hand-tinting a photograph. The presence of hand-tinting reminds us that the glorious tradition of miniature painting was not replaced by photography in India so much as teamed with it. Here, the meticulously detailed jewellery on the female sitter turns out to be the same as that worn by the artist who is seen painting it. Did the jewellery belong to the studio, to lend a certain social cachet to the fee-paying sitters? It seems likely. In Europe, gilding the photographic lily by hand-tinting fell (under modernist pressure) to the status of tastelessness. In India, not so.

To demonstrate that a separate photographic culture exists in India is the point of the show, and it does that well. It is to be hoped that it acts as an invitation to others to fill in the gaps, because this show, for all its vastness, is only a tentative beginning of a story that will continue to be told. It’s also a challenge to get full value from a show which achieves a great deal at the ultimate expense of depth