Sony and Konica Minolta will jointly develop digital single lens reflex (SLR) cameras, they said Tuesday.

Single lens reflex cameras use a mirror placed between the lens and the film or image sensor to project the image to the camera's viewfinder. They typically support interchangeable lenses and are generally much faster-responding and more capable than fixed-lens cameras.

The first jointly-developed products are expected on the market in about a year, said Daichi Yamafuji, a spokesman for Sony in Tokyo. He wouldn't say which company made the initial approach.

News of the agreement and the resulting products are likely to intensify competition in what is already one of the most competitive parts of the digital camera market.

Just a couple of years ago the fixed-lens and SLR digital camera markets did not intersect. Unlike simpler fixed-lens cameras that cost a few hundred dollars, digital SLR models typically cost several thousand dollars, confining their use to a relatively small market of professional photographers and serious amateurs.

But competition became fiercer earlier this year when Nikon and Canon, leaders in the digital SLR space, each launched sub-£600 digital SLR cameras. The Nikon D50 and Canon EOS-350D can be bought with a lens for less money than the top-of the-range Sony camera, the DSC-F828.

No wonder then that analysts IDC predicted in April that lower-price digital SLRs essentially mean the end of high-end fixed-lens models like Sony's F828.

The worldwide digital SLR market totaled 2.5 million units in 2004, according to IDC. Sony and Konica Minolta expect this to grow to 3.6 million units this year, they said Tuesday.

Minolta has been producing film-based SLR cameras for many years and the jointly developed models will draw on some of the company's technology, including its Maxxum/Dynax lens mount system. This first appeared on Minolta cameras in 1985 and about 16 million lenses based on the mount have been shipped, the companies said. A key advantage is that it relies on an auto-focus system in the camera body, so as auto-focus technology improves and owners replace their cameras, the lenses can continue to be used and take advantage of improvements.

The joint development will also draw on Konica Minolta's anti-shake technology, and from some of Sony's image sensor, image processing and battery technologies, they said.