In 1947, when the 24-year-old Saul Leiter first saw Henri Cartier-Bresson’s prints at the Museum of Modern Art in New York, photographers were content to be regarded as photographers. Today’s aspirational ideal is “artist” or “artist using a camera”. But if Leiter is a consummate artist that is because his talents were uniquely served by – and entirely dependent on – the camera in his hand. 

It’s tempting – and plenty of people have been tempted – to describe this pioneer of early colour photography as “painterly”. The upcoming exhibition Saul Leiter: An Unfinished World at the M K Gallery in Milton Keynes – the largest show of the photographer in the UK to date – includes some of Leiter’s actual paintings. These minor works are the equivalent of Cartier-Bresson’s drawings: of interest only because they were made by a great photographer. Painting – its history and Leiter’s hopes of adding to that ­history – is just background to his signature achievement.

Leiter’s achievement is complicated for several reasons. From the 1950s to the 1980s, he enjoyed some success as a fashion photographer, contributing to publications such as Harper’s Bazaar, Vogue and Elle. But it was the unpaid, personal work to which he devoted himself and by which he set most store. Much of this work was in colour. 

Until the 1970s, the photography world seemed to share Robert Frank’s grouchy insistence that, “Black and white are the colours of photography.” Everything changed in 1976 with the exhibition of William Eggleston at MoMA – the first solo show of colour photo­graphy at the museum. A few ­American photographers had been using colour before then – Helen Levitt most notably – but it was Eggleston who, in the words of the curator John Szarkowski, “really learnt to see in colour”. 

Leiter, though, had taught ­himself to see a different kind of colour, decades earlier. While working in black and white – elliptical and lyrical street scenes, portraits of friends, nudes – he was also, from 1948 onwards, becoming quietly articulate in his own ­language of colour harmony. This work attracted little attention, even after photography embraced the brave new world of post-­Egglestonian colour. 

So, this Pittsburgh-born son of a Talmudic scholar, who left a calling as a rabbi to come to New York in 1946 intending to become a painter, who photographed in colour when serious photography existed only in black and white, continued going quietly about his un-businesslike business, usually within walking distance of his apartment in the East Village. The tip of the wondrous iceberg resulting from his long patience was barely glimpsed until 1992, when, appropriately and ironically, the then 68-year-old was included in a book devoted to the so-called New York School. Being seen in the context of this larger group, which included photographers such as Richard Avedon and Diane Arbus, made it clear that Leiter’s style was entirely his own. 

Unnoticed for 40 years, a Leiter picture became instantly recognisable after the publication of the book Saul Leiter: Early Color, by Steidl, in 2006. This extended delay – which Leiter seems to have regarded without frustration or bitterness – proved fruitful in several ways.

It meant, for starters, that there were many kinds of time in his pictures. They are records of the time when they were taken, but even this truism is not straightforward, since he had a fondness for using out-of-date film; the consequent deterioration was imbued with a desaturated radiance.

Although the places he photographed still existed by the time the pictures saw the light of day, the functions and storefronts had changed, the people in the streets were gone, their clothes fallen out of fashion. So the photographs had a kind of nostalgic immediacy, a contemporaneity that was also retro­spective. Pictures, many of them taken by a young man who was now in his 80s, were simultaneously old and new, revealing a way of seeing that was both ahead of its time and backward-looking. 

The documentary quality that is there in any photograph was always faint in Leiter’s work, but after half a century, it had been reduced still further (no news value whatsoever) and intensified, in the way that ­happens to any kind of relic. At an exact moment – often difficult to establish – a bit of the world looked like this, even as Leiter nudged what he saw to the gentle brink of abstraction. This is brought out by Leiter’s 1957 shot Through Boards, used on the cover of Early Color and on view at the M K Gallery: Rothko’s red-and-black eternity with, in the centre, a band of time-specific information in the form of a street, cars, stores and people.

Resolved contradictions are at the heart of Leiter’s magic. The colours run, slowly, as if not quite fixed. His exteriors are often seen from inside through steamed-up windows – such as Pull, taken around 1960 – or are ­mir­rored by rain-smeared windows. The frantic streets become unhurried, contemplative, framed and there­by internalised by a con­sis­t­ently shaping consciousness. This gives his images a subtle psy­cho­log­ical depth, while – another har­m­on­ious contradiction – the fre­quent use of a telephoto lens flattened the pictorial surface. “The con­cept is interesting,” writes John Ashbery in his 1977 poem “Wet Casements”: 

to see, as though reflected
In streaming windowpanes, the   
look of others through
Their own eyes. A digest of their
correct impressions of
Their self-analytical attitudes 
overlaid by your
Ghostly transparent face.

It seems inappropriate to mention a very English poet in the same breath as Ashbery, but Philip Larkin’s line “snow fell, undated” could serve as a caption for Leiter’s many photos of streets in which snow – the white of black and white in colour! – buries or blurs the identifying features of time and place. In Footprints (c 1950), snow causes the emergent red of an umbrella to blossom as if from a spring that lies both in the future and within vague drifts of memory. 

These blizzards add to the pictures’ felt silence: muted colours doubling the romantic intimacy, the cosiness of the outside observed from within. So the scenes also ­contain our reactions to them or – going back to those expanded notions of time – our reflections on them. The mere act of looking at the pictures places us within them. 

Leiter had a wry sense of how adroitly he’d avoided success and in some ways the neglect may have been a heavily disguised blessing. Would he have been able to keep working in the way he did if he’d been recognised, adequately noticed? Not simply because, on the street, instead of being able to wander the neighbourhood ­discreetly, very quietly, the observer would have been observed by people who spotted the great Leiter at work; more insidiously, he’d have become conscious of doing the Leiter thing. 

If he’d kept showing the same stuff year after year, work that now draws plaudits could have incurred the displeasure of critics eager for change, development, of which, as far as we can see, there is mercifully little. Unlike his peers, Leiter had no shaping legacy. The world did not configure itself around or in reaction to his work; we did not start seeing real-world Leiters ­everywhere – until recently.

Still more time has passed since he was discovered – more snow has fallen, much of it dated – and the way we view Leiter’s photographs, what we see in them, is changing. Most of the work seems more poignantly beautiful than ever – but not all. The nudes have suffered, less because we are obliged to view suspiciously images of women stretched out on beds in suspenders and stockings than because these women are smoking. Ugh! 

There is an irony to Leiter’s fleeting snapshots, which draw us back to the language of paint – to the late-19th-century intimiste French painter Edouard Vuillard, whom Leiter cited as an influence. As a contemporary once remarked of Vuillard, “the element of fantasy” in his work obliged him “to keep to these little panels; it would be impossible for him to go further… If he had to work on a big scale he’d have to be more exact – and what would become of him then?” 

Acclaim came so late to Leiter that the question has only arisen posthumously. Since his death in 2013, at the age of 89, various attempts have been made to ensure his name is writ large – and larger. The danger of bigging him up like this – bigger prints, larger-format books – is that it is at odds with his essential aesthetic and identity. And, of course, he has become a belated influence. Todd Haynes’s film Carol (2015) was so steeped in Leiter’s palette and visual vocabulary, it seemed, at times, like a moving retrospective. Lately, this most local of photographers has, as it were, gone global. The history of photography, meanwhile, has had to be reconfigured around him, to do him justice. But his name, like Vuillard’s, has still to be written small if it is not to obscure itself.

Geoff Dyer’s books on photography, The Ongoing Moment and See/Saw, are published by Canongate; Saul Leiter: An Unfinished World is at the M K Gallery, Milton Keynes (mkgallery.org), from today to June 2