the mamiya 35mm slr homepage - the Prismat-family

This should be Mamiyas first 35mm SLR. It is easy to identify: it is the only Mamiya, where the writing "MAMIYA" is written in form of an arc on the prism. The shutter release button is in the speed dial.
Furthermore I assume, it has an Exakta-bayonet mount.

The Prismat NP, front and rear

Description: Mamiya's first successful 35mm SLR model. It has a surprising bright viewer for those days and an auto-return mirror wasn't common too. In additon Mamiya chose the Exakta bayonet mount with semi-automatic aperture for the NP, so many other lenses could be used. The NP seemed to be good and therefore very attractive as basis for other popular camera manufacturers, see the following chapter Clones. Even Mamyia copied his own model, changed the lens mount and called it Prismat WP.

Some details:

shutter	Horizontal travelling focal-plane shutter, speeds from 1 sec to 1/1000 sec, B and T. On my NP with selected T you can open the shutter with the shutter release button and only close it by turning the shutter speed dial. I don't know whether something is wrong or it is typical Mamiya - perhaps you know the "T-feature" from the RB67.
flash	Two sockets for X or FP synchronisaton on the rear. It is not so comfortable for your nose when used, so Mamiya fortunately changed the design on later camera series. Fastest synchronisation speed is 1/30 sec., to remind you of this, the speeds according to the X-synchronisation are orange on the dial.
size	95x152x58 mm, 650 gr.
misc.	Auto-return mirror, cable release, frame-counter, self-timer, depth-of-field preview, a memo-device for film speed and film length.
non-misc.	No exposure meter, no accessory shoe, no focussing help in the viewer. The aperture remains closed after an exposure.

The rear of a 1.7/58 F.C., the 2,8/135 and a Canon-lens.

Though Mamiya used the Exakta mount (introduced by Ihagee) for the NP, the semi-automatic aperture is unique and not compatible to Exakta Cameras. The aperture mechanism works completely different: When pressing the release button on the NP, a small bolt moves out of the camera body and presses the according button on the lens, (c) in the left picture. After the exposure the aperture remains closed and has to be opened with lever (a). For a depth-of-field preview you can close the aperture with a small release behind (c). The f-stop is locked on those lenses, it can be changed by pressing button (b).
On an Exakta Camera the aperture coupling is at another place, and, you have to press the button on the lens to release the camera. Perhaps you can mount an Exakta lens on the NP (I didn't manage it, but this doesn't mean a lot), but you have to close the aperture manually.

Lenses I heard about:

Mamiya-Sekor 2.8/35 F.C.

Mamiya-Sekor 2.8/48 F.C.

Mamiya-Sekor 1.7/58

Mamiya-Sekor 1.7/58 F.C

Mamiya-Sekor 2.8/135 F.C.

a 1.9/50mm, made by Canon

The clip-on exposure meter and the accessory shoe, the Prismat NP with meter.

Some interesting historical facts, sent in by H. Stone: Nikon introduced its Nikkorex F in 1962, it looks very similar to the Prismat NP and was in fact made by Mamiya. You can see some pictures and plenty informations on cameraquest.com, cameraguild or Nikon itself, not so explicit. The Nikkorex F featured a standard Nikon F lens mount and was the first camera fitted with the new Copal vertical travel metal focal plane shutter. Mamiya even built at least two lenses, called "Nikkorex lens Sekor"! Later on this camera appears as Ricoh Singlex, with Nikon F mount.
A small table with my small knowledge about the NP-clones so far:

brand	modell	2nd name(s)	mount	shutter
Mamiya	Prismat NP	Prismatic (in UK)	Exakta	cloth
Mamiya	Prismat WP		not Exakta, not Nikon F	?
Sears	Towers 32A		Exakta	cloth
Sears	Towers 32B		Exakta	cloth
Sears	Towers 37A		Exakta	cloth
?	Reflexa		Exakta	cloth
Argus	?		not Exakta, not Nikon F	cloth
Nikon	Nikkorex F	Nikkor J (in G)	Nikon F	metall
Ricoh	Singlex		Nikon F	metall
Sears	SLII		Nikon F	metall
shutter: curtains made of cloth, travelling horizontal, or made of metall, travelling vertical.

Some Pictures, sent by Bill Salati.

Meanwhile I think, there are at least two versions of one model - a helpful reader knew the difference: the first one with the exposure-meter-element of Selenium on the prism is the PH. It was substituted by the CPH (second picture) with the more progressive CdS-meter, visible beneath the rewind knob.

Description: The very characteristic feature of this model is the leaf-shutter between mirror and lens. This shutter is built into the camera-body and not into the lens. The lens is interchangeable and mounted with a bayonet. In order to look through the viewer the leaf-shutter must be opened, so there is an "assistance-shutter" behind the mirror. It is a focal-plane shutter with one curtain.
It is hard to find a running PH, because the cocking-mechanism of the shutter is very damageable and is often broken. So pull the film advance lever always gently!

Technical data:

shutter	Leaf-shutter, speeds from 1 sec. to 1/500 sec, B and T, shutter speed dial is around the bajonet.
lenses	MAMIYA-SEKOR F. C. 1:1,9 f=48mm, filtersize 52mm. Other lenses: 3.5/38 and 3.5/100.
exposure meter	PH: Selenium type, coupled, with needle in the viewer, film speed from 6 to 800 ASA.
flash synchronisation	V, X and M, one switchable plug and a connection to hot-shoe.

A view at the truly strange bajonet of the Prismat PH/CPH. The leaf-shutter is built-in in this mount.

There are two names for similar Mamiya camera again. Both pictures above show a CWP. I think, the CP is a slightly different version of the same model.
I am very grateful, that Ron Herron sent me plenty of informations about this camera, so that I could make the following summary.

Description:The CWP-Camera is clearly the predecessor of the TL-models. The shape is nearly the same, as well as it has an M42 lens mount, but the concept of exposure metering is very different. The CP/CWP has no TTL-metering, with following consequences:

-	the photo sensor resides outside the body (the small window beneath the shutter release)
-	for metering the aperture mustn't be closed, respectively the selected aperture is not transferred from the lens to the body automatically
-	so the meter is not coupled to the diaphragm. The metered f-stop is indicated in a small window (see picture) on the top and must be transferred manually.

Lenses: they are labelled with "MAMIYA-SEKOR" (with dash instead of slash), with no additional designation other than serial number, focal length and aperture. They have a feature, that later Mamiya M42-lenses don't have: an "M/A-switch". In position M the diaphragm is closed to the preselected f-stop. In position A the diaphragm remains open until the shutter is released. This lever can be used for depth-of-field-preview.
Known lenses are: 2.8/28, 2.8/35, 1.7/50, 2.8/135 4.5/200 and a 6.3/400.

The CP/CWP has a focal-plane shutter, speeds are from 1 second to 1/1000 second, and include T and B settings.

The flash fittings on the CP/CWP are labeled FP and X and are color-coded speeds on the shutter speed dial. FP (green) can be used with speeds 1/1000 to 1/60 sec. using focal plane flash bulbs. X (orange) is for electronic flash or F and M class flash bulbs, and synchs between 1/30 - 1 sec.