Ansel Adams, National Maritime Museum, Greenwich/ Cartier-Bresson: A Question of Colour, Somerset House, review Almost everything is representative of Adams's signature style. He had a meticulous sense of composition, as well as a proclivity for dramatic tonal contrasts. Above all, he favoured a heightened precision of focus that is considerably sharper than the human eye. Typically, his depth of field is large, meaning that things which are miles apart in reality appear with equal clarity. Foreground and background are both crystal clear. In this, Adams was pursuing an avant-garde strategy. Inspired by modernists such as Paul Strand, Adams set himself apart from the "pictorialist" photographers whose soft-focus, impressionistic images had been in vogue before the First World War. Rather than imitate painterly effects, he prized the camera's mechanical capacities. In 1932, along with six other photographers including Edward Weston, Adams founded Group f/64. The name refers to the smallest aperture setting on a large format camera, rendering maximum depth of field. In other words, as curator Phillip Prodger explains in his elegant catalogue essay, "The idea behind Group f/64 was to make pictures the way the camera sees, not the way the human eye does." The effects could be ravishing. Take one of the strongest photographs in the show: Maroon Bells, Near Aspen, Colorado (1951). We are in the Elk Mountains. The view is dominated by the twin peaks of the Maroon Bells, each one higher than 14,000ft. In the middle distance, gentler slopes studded with conifer trees cradle the mountains behind. In the foreground, we see a tranquil lake, reflecting the scene above. The quality of the print is magnificent. On the flanks of the mountains, snowfall creates the illusion of rocky striations that look like velvety graphite marks made by a master draughtsman. These horizontal bands are offset by the verticality of the trees below. The fluffy clouds and adamantine polish of the lake offer more textures to captivate the eye. All the while, the grace notes of the surface elements are underscored by the bold, swelling rhythms of the composition. As a result, the intricate, bejewelled effect doesn't feel over-elaborate, because the underlying structure is so rugged and self-assured. We are offered a rich, sensuous vision of nature's immensity, carefully constructed by an artist's eye. Well, here we move into the subjective realm of personal taste - but let me come right out and say it: I find Adams's aesthetic curiously off-putting. Perhaps the most distinctive thing about his vistas is that they are always empty. It's weird. In reality he was a gregarious chap who loved nothing more than hiking off into the wilderness with a big group and enjoying a few drinks around the campfire. But when it came to art he rarely photographed people. Tellingly, the exhibition contains one of his favourite photographs, which he kept above his desk: a view of the Golden Gate entrance to San Francisco Bay before the suspension bridge had been built. Man's mastery over the natural world is anathema to Adams. There is an irony here: many of his most famous pictures were made not by trekking for days into the middle of nowhere but by stopping his car on a well-known road. Looking at his work, you'd never guess at the vicinity of Tarmac. In this show, there is barely any trace of humanity at all, aside from a picture of a pair of churches, one of a barn-like building on Cape Cod (prefiguring the frontal photographs of industrial structures by the German artists Bernd and Hilla Becher), and a few images of fragments from a shipwreck. Otherwise we are invited to marvel at the pristine majesty of the natural world. But since the eye of his camera sees more than our own, Adams's photographs have an enamelled over-intensity that can feel inhuman. In his pictures, Adams presents an alternative to reality. With consummate skill, he isolates and composes a scene so that it resembles a snapshot of perfection. Yet it also remains distant and unattainable. Even a familiar image such as Clearing Winter Storm, Yosemite National Park, California (about 1937) has an extraterrestrial quality: all that wintry vapour could be clouds of nebular gas coalescing into a faraway planet at the beginning of the universe. On such a cosmic scale, humans are irrelevant. Adams's vision is at best detached, at worst cold and misanthropic. This is the opposite of what he was hoping to achieve. Adams wanted viewers to throb with the same expansive emotions that he experienced while taking photographs out in the field. Yet in this regard his rigorous interest in form has a deadening effect: rather than being swept away by the drama of, say, Waterwheel Falls, Yosemite National Park, California (about 1948), we automatically start analysing the image - noticing the intersecting diagonals around which it has been organised, reflecting upon the contrast of the hard, black rocks in the foreground with the turbulent spray of the white water, and so on. As a result, though I greatly admire Adams's artistry, I rarely warm to him. Cartier-Bresson: A Question of Colour, the inaugural exhibition of philanthropic photography project Positive View Foundation at Somerset House, could not be more different. Instead of wilderness, we see the city; in place of timeless vistas, we have the blink-and-you'll-miss-it immediacy of street photography and photojournalism. Curator William Ewing's conceit for the exhibition initially seems perverse: he juxtaposes 10 little-known, black-and-white photographs by the French modernist Henri Cartier-Bresson, who was sceptical that colour photography could ever be considered fine art, with work by 15 photographers who relish working in colour. The common ground is the concept of the "decisive moment," the English title of Cartier-Bresson's photography book of 1952. With one exception, the photographs by Cartier-Bresson were taken in America between 1946 and 1947. They are tough images about the toil of ordinary life in New York, Chicago and elsewhere. An amputee hobbles round a dirty street corner; a bald man is slumped at a table in a Brooklyn diner; a glum lady with a bandage over one eye stares out of a car window. Here is a nation of grafters and paupers battered by war and barely scraping by. We see hardship and poverty in some of the other work on display. But we also encounter much else besides. I was drawn to the drive-by photographs of the American Karl Baden, who is unknown in this country. Baden records scenes that he encounters in his car: the grey interior of the passenger door often frames what's going on outside. His pictures are extremely charismatic - which, given the drabness of the vehicle, is no mean feat. In general, Ewing selects colour photographers with a zappy, pop-cultural sensibility - such as Robert Walker, who discovers complex nudes and still lifes among the neon signage of Times Square in New York. Together, these photographers feel optimistic, gung-ho, and full of life. You'd have to be dead not to feed off the energy contained within this exhibition. Ansel Adams from Nov 9 until April 28; information: 020 8858 4422; rating: three stars Cartier-Bresson from Nov 8 until Jan 27; information: 020 7845 4600; rating: four stars Follow Telegraph Art on Twitter