A drastic change of image: Magnum photographer Elliott Erwitt has crafted a glorious alter ego

Who exactly is the self-regarding photographer André S. Solidor? Eccentric self portraits reveal him wearing a beret and sunglasses, with a naked lady standing behind him like a lemon, as well as cycling with a baguette tied to the back of his children's bicycle, complete with stabilisers.

He is, as his devotees will know, the famous Magnum photographer Elliott Erwitt, now in his 80s, who is far better known for his documentary photographs of ironic or absurd situations – as well as his portraits of Hollywood film stars in the 1950s and his photo journalism, in which he captured major historic events.

A favourite subject is dogs. He's published many photographic books, with titles ranging from Son of Bitch (1974), Dog Dogs (1998), Woof (2005) and Elliott Erwitt's Dogs (2008).

In a dynamic departure from his usual work, Erwitt has become the Sacha Baron Cohen of the photographic world. He is masquerading as a pompous French photographer, who takes pretentious arty images.

"His initials spell Ass, which is more or less how I consider him," says Erwitt. "He is a contemporary artist, from one of the French colonies in the Caribbean, I forget which one."

As part of a campaign against pretension of all kinds, Erwitt has invented the persona of Solidor to "satirise the kooky excesses of contemporary photography" and "the art world". "I've always been a little suspicious of the art world anyway. I always thought that a lot of the art is simply what you can get away with."

Images include ridiculous smoking fish heads, while gratuitous nudity becomes the norm, with pictures such as Metaphysical Reflection showing a naked woman reflected in a pool of azure water. "Well, that sums up Solidor," says Erwitt. Homage to Cindy Sherman, who typically photographs herself in a variety of costumes, reveals a man with a paper bag on his head; the Homage to Helmut Newton; Ophelia, inspired by Shakespeare's Hamlet depicts a naked mannequin with huge breasts, split in half, floating in the river. "It's good clean fun. That's all. It doesn't hurt anybody," he says.

Erwitt hired outfits from a theatrical costume house in New York for the shoots. He also, as Solidor, dressed up in native costume as a Spanish matador, an Italian priest and a British gentleman out shooting. "I enjoyed dressing up to personify Solidor. It's just a feeling. The attitude, the way he is dressed, the way he presents himself as a pompous, pretentious, silly person." It's not the first time Erwitt has used a pseudo name – he would adopt different titles when he was on jobs he didn't want to be associated with. "I had the name Snaps Picazo when I did restaurant and travel assignments for magazines."

The exhibition, based on his latest book, The Art of Andre S. Solidor (2009), opens this month in London and will be hosted by the designer Paul Smith. It's the first time these pictures have been shown in the UK. A second show, Sequentially Yours Photo Sequences or Indecisive Moments, opens next week at London's Atlas Gallery.

The popular photographic comic strips of the latter exhibition unfold playfully like film stills, which he took in his spare time. "I generally carry my own personal camera when I work on assignments and take pictures as I see them."

Sequences include Cannes, France, 1975, which shows two people sitting in a row of deck chairs – and then the same chairs empty and flapping in the wind. St Tropez, France, 1979 consists of three frames showing a woman putting flowers at a grave, with a dog, who in the final sequence rolls on his back playfully.

The three frames of Mexico, 1973 depict a man sitting on the beach with a woman lying on the sand – until they lie together, with his head on her back. Marilyn Monroe is shown on the set of Some Like It Hot, in a sequence of six photographs showing her dress lifting up in the wind.

Born to Russian parents in Paris in 1928, Erwitt spent his childhood in Milan before moving to America. As a teenager in Los Angeles, he started taking photographs and worked in a commercial darkroom. "I remember one of my earliest published photographs I took was in 1946 of a Chihuahua, next to a lady's shoes," he says.

In 1948 he moved to New York where he took film classes. Then he was drafted in to the US Army for military service in 1951, where he undertook photographic duties while stationed in New Jersey, France and Germany.

He joined Magnum in 1953 at the invitation of Robert Capa. But one of his greatest mentors was Gjon Mili, a Life magazine photographer. "He isn't well-known but he is a very important photographer, who developed the strobe light. I shared a studio with him and he was very important in my photographic life. I learned a lot from him: discipline, photography, the technical aspect – everything."

Erwitt has also made films and documentaries, including Arthur Penn: the Director in 1970 and the prize-winning Glassmakers of Herat in 1977, as well as numerous comedy films in the 1980s.

He currently lives in New York and has a Cairn Terrier called Sammy. "He is identical to Toto from The Wizard of Oz," says Erwitt. "He is quite old and blind and deaf – but he still has some character left."

What attracts him to taking pictures of dogs? "They are everywhere, they are sympathetic and they don't ask for prints. I like them. They are a good subject. They are rather universal and the same the world over."

Next he has a major retrospective at New York's International Center of Photography (ICP) in May. "I'm a professional photographer and then I do photography as a hobby on the side. The two things are quite different. Solidor and these sequences are playful – part of what I do as a hobby."

The Art of André S Solidor AKA Elliott Erwitt, Paul Smith, London W1 (0207 493 4565) 24 February to 26 March. Sequentially Yours, Atlas Gallery, London W1 (020 7224 4192) 16 February to 19 March. Elliott Erwitt will be in conversation at the Cochrane Theatre, London WC1 (020 7269 1606) 21 February