This is my second Mamiya – my other is the Mamiya Korvette. The Korvette was a fixed lens SLR similar to the Zeiss Ikon Contaflex and Voigtlander Bessomatic. This 500 DTL is a more ‘standard’ SLR with an M42 (Praktica, Pentax) lens mount. Top plate layout is as you would expect: film advance, frame counter, shutter speed/film speed selector, pentaprism hump and rewind crank in that order (but no accessory shoe). In 1970, Wallace Heaton (a photographic retailer in London) was offering this 500DTL for £114-19-7 with a ƒ/2 kit lens.
lens: none
focal length: n/a
apertures: n/a
focus range: n/a
lens fitting: M42 (Praktica/Pentax)
shutter: cloth focal plane
speeds: 1 s to 1/500 s
flash: 2 x PC sockets
film size: 35 mm
Underneath the top plate, things are different. This is one of the very few cameras where I have needed to read the manual in order to suss out how things work. When not in use, the film advanced lever is against the camera body and the light meter is switched off. To use the camera, you need to pull out the film advance lever to its standby position – about 30° away from the body. At this point, the light meter electronics are live.
The meter needs a bit of discussion as it is very different to other cameras of its era. In the 21st century, we expect our cameras to have many options with a plethora of buttons and dials and menus. In the 1960s life was very different. You got a light meter (or not). It used one system for measuring the light. You were stuck with the ISO of the film you had in the camera. This meant that photography needed a lot more planning than we are used to today. The light meter in this camera has options – the first to offer these options as far as I know.
The first option is spot metering. Asahi’s Pentax Spotmatic implied that it used spot metering but it didn’t. This was probably the first SLR to offer spot metering. In the viewfinder there is a marked square in the middle of the bottom with an ‘S’ in it. This is the area of the spot meter uses – it is necessary to meter using the square over the critical area of the image and then recompose the image after setting the exposure. There is a single CdS sensor behind the mirror. If there are no critical areas in the image, you can use averaging metering. There are no defined areas for this – metering is by two CdS sensors, one on either side of the image in the pentaprism.
Once you have selected spot or averaging meeting metering, the process is the same. This is basically a shutter priority system merely because it is not easy to adjust shutter speed with the camera to your eye.
To activate the meter, you press the film advance lever in towards the body against a spring. Then you adjust the aperture until the needle is centred on the back-to-front C. At this age, the meter needs to have the aperture at the shooting value (stop-down metering) so the image in the viewfinder can get rather dark and the reversed C hard to see. This was a common fault with TTL metering at the time. The camera uses automatic lenses (automatic here means that the aperture closes down as you take the shot. Focus is still manual). When you press the film advance lever in, a plate just inside the lens mount moves forward and presses a pin on on the lens to close the aperture. I am testing the camera with a Russian Helios 44-2 lens which is a preset lens. To switch between spot and averaging metering, there is a switch on the lower left side of lens mount. When you switched to S, a pointer moves in the viewfinder to the S in the spot metering box and when you switch to A the pointer moves to the A on the right of the box.
The film advance lever has several functions. The obvious one is advancing the film. Secondly, it switches on the metering circuits by being pulled away from the body. Thirdly, it takes a meter reading when pushed towards the body. There is fourth function: fourthly, the centre of the film advance lever is an off switch – pressing this returns the film advance lever to its position close the body and switches off the electronics. Shutter speeds are selected by rotating the speed selector knob. This offers speeds for one second to 1/500 of a second (the sister model, 1000 DTL, had 1/1000 seconds as well). Film speed is selected by lifting the speed selector knob and turning. Speeds available are 15DIN/50ASA to 27DIN/400ASA. In the 1960s this was a sensible range. Kodak slide film was 64 ASA and only specialist film was faster than 400 ASA. Films film speed can be selected in 1/3 stop increments which is equal to 1 DIN steps.
The frame counter counts up from S – when you waste two frames to get to unexposed film it will be on 1. It will automatically be set to S when you open the back.
As I mentioned in my introduction, the lens mount is M42 threaded mount (M42 means 42 mm diameter and 1 mm thread pitch). This means that there are a vast number of lenses available from many makers. Downside is the variety. There are few M42 zoom lenses and those that were made were not very good. Same goes for long focal length lenses – they were made but are rare.
On the side of the lens mount are two PC sockets for flash. The top one is for ‘focal plane’ flashbulbs and is marked FP. The lower one is for electronic flash and is marked X. Both require the shutter speed to be set to 1/60th of a second. The reason a slow shutter speed is required is because the shutter opens as a travelling slit. In order for all the image to be exposed to the flash, the shutter must be completely open when the flash fires (i.e. the width of the slit is the width of the film gate). A speed slower than 1/60 of a second can also be used.
This camera could also be used with ‘M’ class flashbulbs but these take time to reach their full brightness. These have to be used at 1/30 of the second or slower. The flash will then be fired after 1/60th of the second and the bulb has a further 1/60 of a second to reach full brightness. This is academic as ‘M’ class bulbs are no longer available (as far as I know). Below the PC sockets is the switch to change between Spot and Averaging metering.
The base plate has a battery holder which takes one button battery size. I’m using a hearing aid battery which is working well. There is also the button to disengage the film advance mechanism to allow the film to be rewound into the cassette. There is a tripod socket – 1/4 inch UNC.
The back of the camera unlocks by a slide on the left side. Inside is as usual. The film cassette goes on the left and the (fixed) take up spool is on the right. This take-up spool rotates clockwise so the film is wound with the emulsion side outermost.
In use.
My first comment has to be that this is an old Japanese camera. This means that the openings rely on foam lights seals to keep the camera light-proof. These foam seals have long turned to a sticky black goo. Fortunately, this is a simple thing to rectify. First, I scraped out the bulk of the ex-foam from the channels it sits in. Then I removed the residue with a cotton bud soaked in naphtha. I have a stock of self-adhesive foam sheets from which I cut thin strips to fit into the channels the goo came from. The last bit is to replace the foam on the edge of the focus screen inside the lens mount. This last acts as a buffer for when the mirror flips out of the way as the picture is taken.
Having done this, I have loaded the camera with Agfa Vista+ film. When I bought the camera, the state of the outside strongly suggested that it was stored in a shed or garage for a few years. This part, the outside, is easy to clean (Brasso and ROR). Not so easy to clean are the electrical contacts in the meter system. These are in the film advance lever as you press it towards body to switch on the meter and also in the shutter speed selector to allow the meter to determine the set shutters speed. Both of these are a bit hit and mission my camera, and I have to repeatedly push the advance lever in and release it to get any life from the meter and also have to repeatedly change the shutter speed for the same reason.
Focusing is quite easy with the micro-prism centre. It would be easier if there was a split image centre but the focus screen as supplied is fine.
The following is an advert for this camera from the 1971/2 Wallace Heaton catalogue:
Test film.
The test film has been shot and developed. The lens was my old Helios 44 and has performed as expected. The test film shows that there are no light leaks and the focal plane shutter is working as intended. All the shots are evenly exposed.
I have used a mixture of spot and average metering and the film is properly exposed. You cannot actually tell this from the film scans as scanning will correct a multitude of sins, but looking at the negatives, the image density is what I would expect from a well exposed film.
I am well pleasaed with this camera. Here are a selection of images from the test film (the film is my usual Agfa Vista+ film, developed and scanned by Snappy Snaps in Lincoln):
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John's Cameras. A collection of interesting and old cameras. 
I had one of these once, with a dead meter. I never shot it; I just sold it. I kind of wish I shot one roll through it and metered manually. It felt solidly built and it operated smoothly. I’ve since looked for one with a working meter but have not yet been lucky.
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