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Mamiya, Prismat CPH, 35mm SLR camera, c1963

Mamiya 35mm SLRs are a little uncommon as Mamiya is rather better known for its professional range of medium format TLR cameras. Although the company did produce a couple of SLR prototypes in the mid 1950s, it wasn't until 1961 that their first production 35mm SLR (the Prismat NP) found its way to the public.

That camera had a focal plane shutter, however, the same year they released the Prismat PH, an SLR with a leaf shutter, ahead of the mirror. This was the ancestor to the CPH seen here, which arrived around 1963. Essentially the same camera, the CPH had a CdS meter instead of the earlier selenium cell type and the lens mount is different too. The meter was powered by an RPX625 battery, these are now banned due to their mercury content. Take a peek inside!

Mamiya, Prismat CPH, 35mm SLR camera, c1963
Mamiya chose not to put too many markings on these early cameras, to give collectors a wild goose chase later. They didn't sell in vast numbers and are a bit of a rare curiosity today.

The fantastic majority of SLRs have focal plane shutters, however a few have leaf (diaphragm) shutters. The principle reason was the ability to synchronise the shutter with flash at all speeds. It also absolved the maker from making a shutter, as this technology could be bought in, as in the case of the Kodak Reflex series using Compur shutters. Since the shutter must be open to focus the camera, the inside will be flooded with light and the film would be fogged, were a retractable hatch not fitted to protect the film. So there is a degree of complexity to overcome, as there is a shutter, mirror and film protection hatch to synchronise precisely. Mamiya solved this challenge very elegantly... much more so than the Kodak Reflex. At the same time, they also built it so that the mirror returned automatically at the end of the exposure. The starting point is the Seikosha SLV shutter used. Unlike the Compur it takes its cocking drive at the bottom, greatly simplifying the wind on train. Also the release ring is very nicely arranged. The main initiating spring also drives the rear hatch , mirror up mechanism and auto stop down. A separate spring, tensioned during wind on, returns the mirror and hatch a fraction of a second after the shutter closes, then returns the release ring back to the starting point to open the leaves once more. All told it's beautifully made and fairly robust. The springs involved are fairly robust too, so the operation is far from silent, as there is a significant amount of hardware flying around inside the body. Ultimately, all this type of camera proved delicate in service and failures are not uncommon, the benefits of the shutter synchronisation didn't justify the difficulties and the leaf diaphragm 35mm SLR died out in the 1960s. Finding a fully working example today is fairly uncommon. Although build quality is excellent, Mamiya were stretching things a little too far, quite literally, with the top housing. It's a very deep pressing with tell tale rippling . This example was generously donated in July 2009, by Mr. A. Newman. It had a number of issues and was given an epic rebuild to get it fully functioning.

Serial No. 15613
Shutter, Diaphragm type, Seikosha SLV, speeds T, 1, 2, 4, 8, 15, 30, 60, 125, 250 & 500th
(the T setting has to be closed using a button directly under the film speed dial)
Lens, Mamiya Sekor 48mm f/1.9, No. 1058227
Condition, 5F

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