"The hunt for and discovery of an image has always been more important and exciting than its acquisition," reflects Michael Hoppen, a long-time collector of photography, whose highly regarded west London gallery celebrates its 20th anniversary this month. To mark this milestone he's staging his largest exhibition to date, Finders Keepers: A Survey of Collecting, which runs across all three floors of his space in Chelsea. Including more than 130 works, it's a snapshot of the personal treasure trove he has been building for more than three decades. 

"I started in around 1980," he recalls. "I simply saw things I liked and felt I could afford them." One of his first purchases demonstrated his knack for spotting the commercial potential of photographic art, purchasing four William Eggleston dye-transfer prints in New York for less than $200 each - a pretty good investment given that, in March this year, 36 of the American photographer's digital pigment prints were auctioned off by Christie's, fetching $5.9m.

And in the 20 years since opening his gallery, having first set up studio as a commercial photographer in 1980, this nous has helped him flourish within the London art market, despite its notorious reticence towards photography. He was able to add two further exhibition floors and to venture into more contemporary works at the turn of the millennium.

Interior shot of the Michael Hoppen Gallery, courtesy of Michael Hoppen Gallery.

Hoppen now represents work from 143 photographers and their estates - from Hiroshi Sugimoto and Boris Savelev, to younger names such as Lucas Foglia and Alex Prager. He has always chosen to exhibit what he likes and says he has usually bought, or plans to buy, prints by the artists he shows. The prevalence of artists such as Nobuyushi Araki, Daido Moriyama, Kishin Shinoyama and Shomei Tomatsu amongst his roster clearly reflects his love affair with Japanese photography. "They are just so good at what they do, and they make wonderful prints," he says. "There is also a part of me that likes the exotic and I am always intrigued by things I don't understand."

The London scene is very different now to when Hoppen started; Tate Modern opened a major exhibition devoted to William Klein and Daido Moriyama this autumn, while blue chip galleries such as David Zwirner and Pace are opening up in the capital, and Frieze welcomes a broad range of photography in its Contemporary and Masters fairs (though it still doesn't accept photography-only galleries). 

Nude Study, 1870, unknown photographer. Courtesy of Michael Hoppen Gallery.

"I think it has come a long, long way over the past 20 years," says Hoppen. "It's been very gratifying to see Nicholas Serota admitting that the Tate made an error in ignoring photography for so long. With all the museums we now have championing photography, I think London will become a major force to be reckoned with over the coming years."

He adds that keeping overheads down is a key challenge for any business these days, and is sad to see both Diemar/Noble and Foto8 gallery shut up shop this year. Even so, he believes medium-specific galleries still have a place in London, because "that's where you find the expertise". For him, a lack of knowledge about photographic processes or historical references can be a problem for some contemporary art galleries handling photography, and this observation has encouraged him to stick to what he knows. "A photography gallery is just like sculpture or installation," he says. "I have often wanted to show paintings and so on, but feel we need to remain specialists."

Finders Keepers: A Survey of Collecting is on show at the Michael Hoppen Gallery from 12 December until 02 February 2013.

Visit www.michaelhoppengallery.com.

Michael Hoppen, 2004. Image © Neil Setchfield.