Christian Peterson, associate photo curator at the Minneapolis Institute of Arts, has resigned a post he has held since 1980 and plans to leave the musuem Sept. 30.

"It's my choice and my timing," Peterson said Monday afternoon. "You could say that my mortgage is going to be paid off and that allowed me to move forward with something I've been thinking about for some time."

Peterson, 58, plans to remain in Minneapolis where he will pursue personal photo research and book projects. His last show at the museum, "Wide/Eyed: Panoramic Photographs," will open Sept. 15 and run through Feb. 27, 2012.

In his decades at the Institute, Peterson has organized innumerable exhibitions and written more than 20 books and catalogs including Masterpiece Photographs from the Minneapolis Institute of Arts, and After the Photo-Secession: American Pictorial Photography, 1910 - 1955 (published by W. W. Norton in 1997). His other exhibitions include The Poetics of Vision: Photographs from the Collection of Harry M. Drake and Peter Henry Emerson and American Naturalistic Photography.

His current show, Facing the Lens: Portraits of Photographers, including many images by Minnesota artists, is on view through August 28.

As a long-time colleague of the late Ted Hartwell, founding curator of the museum's photo collection, Peterson helped build the museum's 10,500 piece photography collection which is strong on classic black-and-white documentary images, Magnum pictures, and work in the Ansel Adams/ Edward Weston and Walker Evans traditions.

"Christian and Ted really built the collection and it's sad to have this transition occur, but I hope that Christian will come back here to teach people about the collection because he's very, very good in the classroom," said David E. Little, the MIA photo curator. "One of the things that's so great about Christian is that he has such incredible knowledge about both the history of photography and this collection."

Peterson is especially known for his interest in Victorian-era imagery and pictorialist work by members of camera clubs. He also collected photo ephemera (brochures, announcements) for the museum, and was a champion of those often overlooked but skilled 19th century amateurs who pioneered the genre when it was still an experimental medium.

"I did do a lot of work with pictorial photography and most people pigeonhole me as doing only that, but that's not the case," said Peterson. His favorite and most important show was "After the Photo Secession." It's "very gratifying" that the book is still the standard reference after more than a decade, he said.

The museum will launch a national search to fill Peterson's post. "I really want someone who will be very adventurous with the collection and able to rediscover the history of photography and to rethink the masterpieces that we've seen over and over again," Little said.