A 35mm film SLR system that added TTL open-aperture metering compared to the earlier Mamiya DTL series cameras. It consisted of the following models:
- MSX 500 - a SLR with automatic-aperture variation of the M42 screw mount plus the aperture indexing pin needed for TTL open-aperture metering, top shutter speed of 1/500th of a second, TTL spot light metering, match needle system in the viewfinder, without a hot shoe and a self timer;
- MSX 1000 - a MSX 500 with top shutter speed of 1/1000th of a second, built-in hot shoe and a self-timer;
- DSX 500 - a MSX 500 with two separate TTL metering systems selected by a switch beside the lens mount: spot for reading just 6% of the total picture and average for full area light measuring. The hot shoe was built-in this time;
- DSX 1000 - a DSX 500 with top shutter speed of 1/1000th of a second and a self-timer.
Mamiya produced an extensive range of Mamiya/Sekor SX lenses for this system, from the fisheye 14mm and ultra-wide angle 21mm to the super telephoto 800mm. Most of them had automatic diaphragm, and only the 60/2.8 Macro, 600/8 and 800/8 were equipped with preset diaphragms.