The Mamiya M645 1000S is a medium format SLR camera that was introduced in 1976. It is an upgrade to the original M645 model, featuring a faster top shutter speed of 1/1000th of a second, a self-timer, and a depth of field preview button. The camera uses 120 or 220 film, offering 15 or 30 exposures respectively. It has an interchangeable finder system, allowing for various prism and waist-level viewfinders, and interchangeable focusing screens. The M645 1000S utilizes a moving coil electronic focal plane shutter and has an instant return, automatic mirror system with mirror lock-up. It is powered by a 6V silver-oxide PX28 battery.