Of compulsive nature: Pentaflex 8 – (Part 1)

Of compulsive nature: Pentaflex 8 – (Part 1)

Of compulsive nature: Pentaflex 8 – (Part 1)

The examined camera has the serial number 35933; With Pentovar, No. 6355608. On the back of the selenium cell I find as confirmation “ELECTROCELL Dec”. Stamped in 1963. The production year can therefore be derived from the serial number. On the inside of the case, the number 1675 is engraved. Series 1, serial number 675.
The cell originates from the “Electrocell-Gesellschaft Falkenthal & Presser”, founded in 1933 Berlin-Dahlem, the moving-coil instrument perhaps from Erlangen.

The new price in 1960 was 1000 Deutschmarks, more than two average monthly wages.
The Pentaflex 8 is a rear loader, which makes it difficult to reach the film gate. Poking around there with a brush without being able to see anything, is an imposition. The film’s side guides need to be checked and cleaned. This is what the film channel looks like, just removed. The rigidly guided claw of the Pentaflex 8 settles in position + 2. I am not aware of any projector with a geometry corresponding to this.

The camera does not take plain reels, you’re forced to use the cassette loader system. It cloeses light-tight when pulled out of the camera. The film consumption display is based in the loader, it can be read through a window in the camera.

The Pentaflex 8 has a single frame counter, which is very good. The downside is that it goes to 77. How dare they?! The connection to “foot” is lost. For 8 mm film, one foot contains 80 images, which beautifully equates to five seconds at 16 fps. The clockwork motor pulls 2.75 metres through, 720 frames or 45 seconds. The going barrel allows winding up while shooting, pretty silent thanks to a claw anchor. The frame numbers are placed directly on it and can be seen through a window in the case. No one has thought about the relationship between the toothing of the going barrel and the film. 143 teeth wouldn’t be necessary. But the gearbox would have needed a recalculation. If you want to equate a barrel turn with 80 teeth, you have to do so without prime-number transmissions. 143 is not a prime number, but contains prime numbers 13 and 11.

If you think the frame rate could be adjusted continuously, you just need to run the camera and turn the speed dial to realize that you were wrong. The mechanism locks in to certain speeds and accelerates or slows down in stages. Inside, there are fixed stops on a cam disk. There are no intermediate values. As a construction, of course, this is frugal, but slightly misleading. A bore, a rest ball, a spring and five round dents in the underlying sheet would provide clarity.
An electric motor can be mounted. There are two threaded sockets in the case. The 1-1 shaft is covered with a slider. A motor carrier must have two M3 screws 90.5 millimeters apart. The shaft has a threaded hole (M2.5) behind Ø 3 × 1.25 and on both sides a groove 1.5 × 2. With an electric drive, any speed up to about 64 fps is possible. The centrifugal force governor gets set to highest speed.


The case’s base is very unfavorably designed. Such a heavy camera would have to have a large footprint. Empty and without optics, it weighs 1390 grams, loaded and with the Pentovar mounted a full 2.1 kg. You want to swap film cartridges, rewind the spring during shooting, or be able to use an electric motor without moving the camera. The actual seating is circular and has a diameter of 20 mm, area about 314 mm2. However, the camera’s baseplate would provide 58mm x 116mm, 6728 mm2 (more than 20 times than what is actually used). The surfaces of the round seating and the rectangular base heel are not at all leveled.

Loctite-secured nut on the opposite side

The Pentaflex 8 is the only 8 mm film camera with a rotating mirror shutter. The Nizo-Heliomatic 8 Reflex, Ercsam-Camex Reflex 8 and Beaulieu Reflex 8 have “up and down” mirror shutters that easily cause uneven exposure over the image height. The camera would be on a par with professional SLR cinema cameras. An indication of the shutter angle can neither be found in the brochure nor in the manual. According to the table in the guide, it would be 172.8 or 177.2 or 184.3 or 192 degrees. Those are very confusing and wrong values!

According to my measurement, it is 50 degrees, so 150 degrees for an image. Due to the oblique erection of the shutter, the effective opening angle is still slightly reduced over the width of the image from left to right, in the projected image from right to left. All these constructions show this slight deviation. It cannot be seen during projection. From the 360º to 150º ratio, the exposure time can be calculated:
2.4 × 16 frames per second = 1/38.4 second; Rounded 1/40, not 1/30.
In the brochure, a 30-fold magnifying optical system is mentioned, which is not true. The magnification of the viewfinder is 15x, at least with the camera I have here. It is an aerial viewfinder, there is no matte screen, as it is stated in the prospectus. At the price of a loss of brightness, a matte screen would provide clearly safe-res sharpening points. The following flaw is in the manual:

Why then a reflex viewfinder? It has to be said: A reflex viewfinder without a matte screen makes any claims about professionalism ridiculous. If you don’t want to have light loss in the viewfinder, you need a split image or microprisming screen. I simply can not answer or explain why no screen has found its way into the Pentaflex 8’s viewfinder. The split image system had long been common knowledge, all patents had expired back then already. The manual on page 5 claims:

The crosshair is not supposed to be sharply mapped, but supposed to be sharpy seen – so much about terminology.

The axial play of the shutter arbor is insidious. There may be focus jumps. It’s all about a tenth of a millimeter.

Washers and a lock washer (arrow) keep the shaft in the desired position, the thickness of the mirror glass is considered by a hundredth of a millimeter. When starting the camera, it can happen that the torque of the spring disc is exceeded, then the sharpness of the viewfinder image disappears. That, according to my measurement, is the case at about 1.5 Newton. With a dormant mechanism, that is when focussing before shooting, there is no problem. Because of the spring tenson, the shutter shaft runs with a bit too much friction.


Then I discover something completely weird. The supporting piece for the shutter- and claw group is dowelled and screw-mounted in an area around the gate (yellow arrows). Otherwise, there is no contact between these mechanical groups. With regard to the gearing of the shutter’s gear and the claw’s gear, this is not a solid construction. A circular rod placed diagonally under the varnish supports the carrier piece at the bottom. One did not rely on sufficiently accurate construction or, more likely, added access to the claw shaft after the pressure cast parts were already available, by the way the same extremely lightweight alloy as for the Pentaka 8.

With the support rod, one could simultaneously adjust the mirror shutter around an undefined horizontal axis, influence the play of the gearing and compensate radial forces acting on the 1-1 shaft. Such an entanglement of objectives is ludicrous, since optical and dynamic-mechanical solutions do not belong together. The bearing carrier would have to be fastened as large as possible, its fine adjustment would have to be discarded if improvements were made during production, or the carrier piece would have to be underlaid. I find pinned cube levering absurd. Bevel gears may have a little more play, there is no problem with that. The difference is that a bevel gear and a straight spur gear are involved at the same time.

The block stops only under the tension of two screws, there is no pinning.

The self-timer relates to the pre-war period, with the Movikon 16 from Zeiss-Ikon. I think it could have been omitted in favor of a more open front.
The Pentaflex, as Marco Kroeger points out, had been planned with a lens turret. Then came the Altix-V-bayonet and over-sized lenses for wide-angle and normal optics. Why Pentacon was not able to lower itself to the D-Mount or the M13 short thread is not clear It would not have deterred from deep-mounted lenses, but instead brought the openness that characterizes professional products. The pressure in the direction of zoom optics was obviously overwhelming at that time. The Agfa-Movex Reflex 8, launched in the same year, also carries a thick, heavy zoom lens. It simply was not tolerable that Berthiot and Angénieux advanced with their zoom lenses. Zeiss also had to have one, a better and faster one. When you see how images are taken with your smart phone today, millions of times, with a tiny lens, f/2.4 or f/2.2, you shake your head. The optical zoom has gone out of fashion.
The system looks to me like an intermediate model for later, even more strongly integrated Super 8 cameras. Painted screws and sheets to mount optical parts in an east-asian manner implies to lose calibration/settings if you completely take the camera apart. But this is essential for thorough cleaning. In order to get to the mirror shutter, one has to take apart the camera pretty far. Service-friendliness is not given for the Pentaflex 8 and the lubrication concept is odd. Plastic gears should run dry or lubricated with water. When they get greased, parts of the grease settle in them, oxidize and start to get sticky at some point. You can hardly get that removed and these plastic gears are no longer available.

The design dates back to the first half of the 1950s. Basically, the Pentaflex 8 is a clockwork motor ARRIFLEX with a three-blade shutter, a screwed lid and loading cartridges. The camera carries is a compulsion for excellence, which is not given. The “international markets” (Kroeger) offered quite some better thought-out product, many good ideas. The queer Movikon 8 provides free access to the film channel, the GIC 8 takes twice the film length, the Camex 8 offers long exposure of single frames, the Bell & Howell Filmo 8 T exact focusing on its matte screen, the Paillard-Bolex H-8 unlimited film movement backwards as well as forwards, the Specto 88 had been running for longer than a minute for ten years, the Japanese Sekonic Dualmatic 8, also from 1963, made inserting a second film superfluous without requiring a cartridge. Of course, if someone in Halle or Zinnowitz on Usedom had asked photographer Walter Adrion about the dualmatic before Christmas 1963, an eyebrow would have been raised on the other side of the counter. I close my eyes when seeing the Pentaflex 8.

At Pentacon, the leadership was distanced from the common people in the same way as anywhere else. Why does one go to school or university? One wants to belong to the upper class, wear a white shirt, collar and a hat, eat roast beef. This can only be achieved with participation, as in the West. The blue plastic and light gray varnish are off, another product of the technology transfer in the cold war has come to light. I am always speechless about the spiritual emptiness of those years, for example in front of a fruit bowl of glass with golden plating on the edges, nothing more than a worm gear with straightened teeth.

Simon Wyss
Simon Wyss

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