By Roman Yarovitsyn
Everyone who uses camera has to make a difficult choice – which one to choose from an ocean of models. Any customer, no matter pro or amateur, navigates by main features and numeric values such as pixel number, ISO range etc.
Exterior design plays an important role as well as the type of lens mount and battery size. But the main part, which controls the most valuable parameters, lies inside and not visible, especially in digital cameras. This is the shutter.
Most customers don’t ever see them. To a greater extent this applies to focal plane shutters covered by CMOS from back and by the mirror from front in DSLRs. Focal plane shutters of most cameras are similar nowadays and these are vertical travelling metal blade shutters, which became a world standard back in the 20th Century.
But it was not always so. Some half a century ago, classic Leica-type shutter with flexible rubberised silk curtains were still installed in most cameras despite the fact that it was inferior to the newer Copal Square shutter.
The reason was the patent restrictions. The rights to release belonged to the consortium of four Japanese companies: Konishiroku, Mamiya, Copal and Asahi Optical. These companies took part in the designing and launching of metal blade shutter in 1961. That’s why no one camera manufacturer held the rights to assemble own shutters of this type.
Even Nippon Kogaku (Nikon) was forced to order in 1962 its competitor Mamiya to produce the Nikkorex F with the Copal Square shutter. Patent restrictions expired in 1981, but there were some camera manufacturers, which realized their own metal blade shutters in SLRs before the patent expiration. There were Eastern Bloc plants behind the Iron Curtain and they didn’t violate patent law. They created their own”Socialist” shutter design.
The first was Pentacon, a unification of three pre-war giants Carl Zeiss, Ernemann and Ihagee which remained in the Soviet occupation zone in Germany. East German designers understood very quickly the value of metal shutters.
Already in June 1961, a year after launch of the Konica F with first-ever metal blade shutter “Hi-Synchro”, in German Democratic Republic a patent 1145474 was issued to Horst Strehle, Günter Heerklotz and Hans Zimmet. They designed a mechanism for moving metal blade curtains in a fundamentally different way to the Japanese. Instead of a pair of parallel levers, crossed ones like scissors are used in the German design.
It’s worth stopping here and explaining how these shutters work and what’s the trick to their operation. Each curtain of such a shutter is comprised of several thin metal blades. They can unfold to close the frame window or fold in a narrow stack to open it. Overall, the shutter mechanism height depends on the number of blades and also their width. The more blades, the smaller each blade. This leads to a smaller open curtains stack above and below the frame window and the overall height of the shutter mechanism can be reduced: this is an important layout point in camera design.
Copal Square curtains were made of four blades and overall dimension of shutter was just two times higher than frame window. German shutter curtains consisted of three blades which inevitably affected its compactness. This is a direct consequence of the design of the lamellas movement levers. And one more peculiarity of German shutter: curtains travel from the top down, but not from bottom to top like Copal. However, by 1968 the design was brought to industrial development and after registering two patents 67026 and 67027 in February, the shutter was adopted by the Praktica L SLR, launched onto the market in 1969.
One of most important specifications was just as good as its Japanese counterpart: a flash sync speed 1/125 sec, a great result for the early 1970s.There were one more intermediate version of the shutter, used in the Pentacon Super SLR in 1967, but the curtains were hybrid half-cloth (in this article we only consider full-metal shutters). The “Praktica shutter” was manufactured almost 20 years and successfully worked in five million L-series SLRs. But in 1987, Pentacon refused it in favour of the Copal system in the Praktica BX-20. Any patent restrictions expired some years ago.
Over the years of production, the shortcomings of this East German shutter have become more apparent. First of all, it was bulky: 64mm high, without mounting lugs, almost triple the height of a 35mm frame. The shutter body width was 71mm, but unlike the Copal all this without timing mechanism. It was mounted as separate unit under the top of the camera.
But one more problem of the East German shutter turned out to be decisive: it was poor choice for modular camera design. Copal shutters were designed separately from other camera systems and can be changed without full disassembly of neighbouring mechanisms. To dismount the Praktica shutter you must disassemble the whole camera: top shield, then the “muzzle” with mirror and pentaprism, the timing plate. Only after that you can get the shutter into your hands.
This is just a description of disassembling the simplest Praktica L. More advanced models with TTL-metering and automation mean flexible printed circuit boards and other electronic items also have to be removed. Moreover, 1/125 sync and 1/1000 top speed were too outdated for the end of the 1980s and the top speeds of the Praktica cameras did not change for years.
East German engineers designed a great shutter, but the insistence by Communist leaders that cheap cameras for workers was a priority played a significant role in Pentacon’s designs lagging behind Western competition.
The path of USSR designers was longer and more winding. Let’s begin with the fact that Soviet Union released metallic focal plane shutter for SLRs as far back as 1935. The camera name was the Sport and experts are still arguing whether this design or the German Exakta was the first-ever 35mm SLR. The name of the inventor was Alexander Gelgar, and after WWII he continued metal shutter designing.
His challenge was the same as Hubert Nerwin when he tried to turn the rangefinder Contax II into the reflex Syntax. The upper drum of the Contax roll-up shutter exactly where the ground glass of the SLR viewfinder had to be. How Nerwin resolved this layout problem we never know, because there aren’t even any drawings left from now mythical Syntax after the Allied bombing of Dresden in 1945. Maybe he found a good solution without changing this complex shutter.
Movie camera designers are lucky: they don’t have the same restrictions when it comes to the camera weight and dimensions
Gelgar faced to more serious problem because the second curtain of the Sport shutter had to climb into the superstructure of the camera during cocking. It was acceptable with an old waist level finder but was impractical once proper SLR pentaprisms were invented.
As a former cameraman and later motion picture engineer of the Soviet Lenfilm studio, Gelgar knew that the best focal plane shutter is a movie camera obturator: a rotary disk with section cut into it. It’s ideal from any point of view: insensitive to heat and frost, simple, cheap and reliable. Moreover, it has a full-frame opening at any speed!
It has only one drawback. It’s huge. The most important shutter specification, usually invisible to ordinary consumers but critical for engineers, is the ratio between overall dimensions of the device and the dimensions of the frame window. Rotary shutter diameter must be at least four times exceeding frame diagonal. The best illustration is the body of the Mercury Univex camera. This rounded top cover is not just decoration for the depth of field table. This is a housing of rotary shutter! You should also note that Univex is a half-frame camera.
Movie camera designers are lucky: they don’t have the same restrictions when it comes to the camera weight and dimensions like those making stills models. If the camera already weighs 100kg, an extra 5kg will not make it much worse. Unfortunately, the design of 35mm SLRs makes such a shutter almost impossible.
Nevertheless rotary disk shutters were used in 35mm photographic cameras and some of them were famous enough: the Olympus Pen F and the Robot, for example. Olympus shutter were synchronised with electronic flash at any speed, up to top speed of 1/500. But these cameras were half-frame. Gelgar figured out how to marry rotary shutter with full-frame compact enough SLR. He turned a disk into the shape of a lady’s fan. In this case the full disk is not needed, and the remaining half cut into separate blades.
These sectors may unfold into the a solid curtain or sit stacked. Just like Copal Square but around axis. In 1958, two years before Hi-Synchro appearance, Gelgar received a copyright certificate number SU114106 for «Затвор обтюраторного типа» (obturator-type shutter). Such a shutter was probably used in almost unknown SLR made by GOMZ in Leningrad. It was announced in the July 1960 issue Soviet Photo magazine in the article by V Kouzmin, an engineer. But this was only a prototype and the new Sport was never created.
Gelgar’s invention was improved by the Ukrainian designer I S Batyuta, which added torsion curtain dampers and received a copyright certificate number SU139189 in 1961. The improved device got the name “fan-bladed shutter” and was used in the Kiev-Automat SLR family from 1964.
Generally, this type of shutter could be considered a completely successful answer to Japanese metal shutter. Sync speed was only 1/60, slower than 1/125 of Copal counterpart, but mechanism already was freed from flexible curtains and ribbons, which were sensitive to cold and unreliable. Soviet self-confidence increased, epseically after sending the first man into space: “We can do better”.
For those dissatisfied with 1/60 sync speed on primitive SLRs, KMZ manufactured the Zenit-4 family with a leaf shutter. It was synchronised with electronic flash up to 1/500. Unlike their East German colleagues Soviet engineers underestimated the prospects of a square-type shutter and were a decade too late in terms of camera development. Soviet photographic industry decided to choose its’ own path of shutter improvement.
Moreover, although Soviet inventors were not spoiled with “bourgeois” royalties, patent restrictions were respected by the USSR on the international market: the export of cameras was one of the most stable sources of hard currency. Dollars were extreme vital for equipping both Soviet civilian and especially military industry.
Soviet designers were sure that they could reach 1/125 sync speed in a shutter with flexible cloth curtains. With the new project, Krasnogorsk engineers decided to eliminate one of the Leica-type shutters’ flaws that photographers usually don’t have a clue about, and which was solved in Copal Square.
This was one of the main reasons behind the attempt to replace the focal plane shutter with a leaf shutter in the late 1950s. Designers of metal blade Copal Square shutter resolved this problem due to pre-overclocking of the curtain’s leading link. The short curtain move played an additional role and Copal shutters expose the frame much more evenly than Leica-type shutters. All this is described in sufficient detail in the article «Фокальные затворы для любительских фотоаппаратов» (Focal plane shutters for amateur cameras) in the February 1972 issue of “Optical-mechanical Industry” magazine.
KMZ designers decided to improve the cloth shutter and make a completely new version which works in the reverse way. They call it a “shutter speed countdown mechanism” versus “direct counting” of a classic shutter.
In ordinary cloth shutters, right after the shutter button is pushed (or mirror raised in SLR), the first curtain starts running, but the second one’s start depends on the shutter speed selected. This way the width of slit between curtains adjusts, providing slower or faster shutter speed. In the new shutter, the starting time of the second curtain stays constant, but the first curtain starts dependent on the speed setting.
You say “that’s impossible”? Just look. Shutter button pushing or mirror raising launches the stabilised rotation of leading drum, which gives the command to start the second curtain at the end of its turn and always after a precisely calibrated period of time. The order to start the first curtain is earlier than the order given to the second curtain. So, at the shortest speeds the whole exposure happens almost at the end of drum rotation. This way the precision of the slit adjustment increases, especially at fast speeds. A designer’s team lead by Ivan Katkov and Tatyana Sinelnikova finished work and got certificate of authorship SU164524 in January 1964.
The Zenit-7 with such a shutter launched in 1967 and Soviet authorities prepared to flood the whole world with the new super shutters and show the Japanese camera industry a thing or two. But something went wrong. The 1/125 sync speed turned out to be unavailable for the cloth shutter, which jammed quickly due to springs being overtensioned. The countdown mechanism turned out to be too complex and capricious.
Only 3,000 Zenit-7s were manufactured and almost all of them broke down during first months of shooting. The drums and wheels of classic shutter are too heavy for fast travelling. The Zenit-7 project was abandoned in 1971, but this shutter got a second chance in the Zenit-16 SLR.
Designers turned it 90 degrees (copyright certificate SU 349347) to provide vertical travelling with less spring tension and curtain speed. Those few who have this camera in still working condition can have fun listening to the sound of the shutter at different speeds. As the slowest speed of this shutter is 1/15, the second curtain starts always just slightly before this time interval after the mirror rises and shutter cycle starts. That’s why the shutter sounds like 1/15 at every speed, even 1/1000.
In the shutter of Zenit-7 this rule worked only until 1/125 sync speed, the slower speeds were provided by the use of a retarding anchor. The shutter of the Zenit-16 was simplified by decreasing the range of slow speed, but it did not improve its reliability. Meanwhile the world was flooded by square shutters with metal blades and it finally dawned on Soviet photo industry managers that the unique Soviet path had led only to a dead end.
Finally, the development of a Soviet version of vertical-travel metal blade shutter started in the early 1970s. Here we step into the realm of espionage, because all the factories involved in these projects were part of the defence industry, so plans and documents about it were classified. Nowadays most participants in these projects are dead and the enterprises are in a state that can be described in one word: “rout”.
To get any information from living people is almost impossible and we can rely only on a few sources, such as internet and magazine articles. The miraculously surviving database of Soviet patents turned out to be a huge help. But the names of some designers are still unknown, just initials in copyright certificates. It would be appropriate here to publish an interview with one of the developers, but since almost all of them have left our world, I have to talk about things that I can only guess about. If any of the readers have more detailed information Kosmo Foto will be happy to publish a sequel based on them.
To understand well how Soviet shutters works I broke three SLRs to get the shutters out and study their design. To be completely honest, they were already broken by someone, I just finished what they started.
The first ever vertical travel metal blade shutter in USSR was installed into Kiev-17 SLR. It was a replacement of the Kiev-15 which had a fan-bladed shutter inspired by Gelgar and Batyuta. It inherited the main fatal flaw. Fan-bladed shutter units remained bulky despite their creators’ efforts: 90mm width. The Kiev-15 is as much of a tank as its predecessor the Kiev-10 which was called “a flatiron” by Soviet photographers.
When the Kiev-17 appeared on Soviet store shelves and photographers started to use it, they were all sure that there is shutter inside similar to Nikkormat or Konica. Somebody like me was a little confused by slightly long sync speed of 1/60 but we attributed this to poor Soviet parts processing. The majority still think the same. But it’s not true. There is absolutely original shutter inside all the Kiev-17 family: the Kiev-19, Kiev-20 and others. Both curtains of this shutter consisted of only two blades. But this is not the only difference of Ukrainian shutter from the others of this type.
If in Japanese and German shutters the curtain blades move on swinging arms and hinge rivets, in the Ukrainian one this can only be said about two auxiliary plates. The main two, so-called slot-forming lamellas, have bent eyes with holes that slide along a guide axis, which is not found in any foreign equivalent.
The need for such a solution can be understood knowing one feature of any focal plane shutters: the edges of both curtains must be strongly parallel to each other and to appropriate frame sides all the way while they are travelling. This depends on the uniformity of exposure especially at the shortest speeds when slit width can be less than a millimeter. In the Japanese shutter such blades movement provides a parallelogram linkage system, as a scissor-type system of the East German shutter. The weakest point of such systems is the hinge rivets attached to the inner surface of the lamellas. This is the most difficult part of the technology for manufacturing such shutters.
Fastening such rivets onto the thinnest plate is fraught with the greatest difficulties. Installing a rivet on one side should not lead to deformation of the lamella, and on the other side the connection should be extremely strong. Rugged enough to withstand hundreds of thousands of acceleration and braking cycles. Soviet designers did not trust the capabilities of their factories too much and reduced the number of such rivets until two, placing them on the least critical blades. Sliding by guiding axis slot-forming lamellas always strictly oriented for proper slit.
But the slide that also fixes the blades’ parallel movement needs lubrication. This means the temperature dependence of shutter, which was successfully overcome in Copal shutter working without lubrication and perfect for cold temperatures. Plus, the sliding rubbing pair kills any dreams of rapid curtains: 1/60 sync speed is not bad at all for such design.
Be that as it may, this design lived for quite a long time and was used even in a professional Soviet SLR, LOMO’s Almaz-103. In this SLR, the Ukrainian shutter was slightly modified and turned upside down, that’s why the curtains travel top down, as in the Praktica. The Almaz was made in Leningrad, and this fact raises the question about shutter origin. Let’s remember that there was Planned Economy in Soviet Union and no one enterprise had exclusive rights for its own developments. Any design could be used in every plant in USSR, so first appearance in Ukrainian camera does not guarantee Arsenal’s authorship.
The patent database only tell us a date of certificate SU 609104 with a publication date of 30 May 1978 and the names of the designers: Anatoly Nosko, Nikolay Bandura, Yakov Zolotarevsky, Leonid Korchnoy and Nikolay Serov. Instead of factory name indicated thus: п/я Х-5827. What does it mean?
Here we must understand one thing, unfamiliar for people not born in the USSR. After WWII any Soviet enterprise, be it a factory, a design bureau or an office for the preparation of horns and hooves had at least two names. One was intended for civilian public using, and another for military secret correspondence. This second name was just number of a postbox to hide the real name and even location from enemy. This “п/я” exactly means “почтовый ящик” that is “post box”.
Only those who worked there and those “in the know” were aware of the true meaning of the numbered boxes. But after USSR crash these numbers were declassified and somebody created even a table to identify enterprises. X-5827 is just”Arsenal” plant in Kiev. That factory manufactured “Kiev” cameras together with equipment for the Soviet military.
Despite the shortcomings the Ukrainian shutter is already fits well into the modular camera construction principle. Remember my description of Praktica disassembling? So the Kiev shutter is removed in no time! Just detach the bottom cover, disconnect cocking thrust and detach two screws. The shutter drops into your hands in seconds! Moreover, the timing mechanism is mounted together with the curtain plate as in the Copal Square shutter. Finally, Kiev shutter can be called “Square” due to overall dimensions: 66mm height and 73mm wide.
But this shutter type was not the only one in USSR, surprisingly. The Zenit-19 shutter dropped to my hands almost the same way, just like the Kiev’s, and I couldn’t believe my eyes. I knew that this shutter is different at least according to number of curtain blades. Three blades in every curtain versus two in the Kiev.
Something completely different surprised me when I understood its operation. Searching the design of Arsenal shutter in the patent database I’ve seen enough different examples. The design of KMZ shutter I flipped through with a grin: what can they come up with on paper! It would be obvious to any mechanical engineer that no-one would produce such a primitive design. But KMZ manufactured at least 150 000 shutters, protected by copyright certificate SU 877462 which was given to Anatoly Padalko and Yury Lyagin at 30 October 1981. The post box “п/я В-8450” specified in the patent application is predictable: this is Krasnogorsk Mechanical Plant.
This design of the «ФЗЛ» (Фокальный затвор ламельный, Focal plane lamella shutter) shutter was not similar to any other. Engineers completely eliminated any complex rivets, extremely simplifying the technology. Each curtain consisted of three blades is driving by one turning lever. The connection was implemented by a bend at the edge of each lamella which moves by two pins fixing it from both sides. Both driving levers are equipped with six pins, which moves three blades by their bends. Levers in their extreme positions parallel to the long side of the frame (curtain opened) or diagonally when the curtain is closed. In the last case, blade bendings line up like a ladder.
But that’s not all! All six blades of both curtains sliding across the frame between two parallel guides. To eliminate the skew, all of them are made as U-shape frame. I couldn’t believe it! How can this even work?!
First of all, the coupling by two pins with such a trajectory of levers is impossible without gaps. Besides the inevitable noise, the sliding friction between pins and bends will fast wear out the mating points until they break down. Even plastic gaskets on the pins will not save shutter from braking out. But the worst thing is the design of curtains. Increased blade height through a U-shape guides forces to lengthen the slide rails and ultimately increase overall height. The rails height of the Zenit-19 shutter is 73mm, this is the biggest so far! But the blades do not deal with the skew because of the gap needed between the U-shape frames and the guide rails for easy sliding.
Any drive levers’ movement slightly skew each U-shape blade which travels in such position all the way. So, friction of the blades between guides and each other must be unbelievable and high travelling speed accompanied by huge loads. There is only one bit of good news: such curtains do not need an effective brake. At the end of the stroke they will simply get stuck in the guides. Imagine a car which can be driven only with pushed down both pedals of gas and brake. This car won’t go far. It is not surprising that these shutters did not last long and the warranty life declared by the factory was only 3,000 cycles. This is the price of refusing hinge rivets.
Any student of my mechanic faculty of the Leningrad Motion Picture Engineers Institute, who proposed something similar, would be deprived of all credits in theoretical mechanics, strength of materials and theory of mechanisms.
And now remember the sound of the Zenit-19 shutter, if you’ve been lucky enough to hear one. It cannot be anything else. At the same time, this shutter is both extremely technologically advanced and as easy to produce as a Kalashnikov assault rifle.
Surely the developers received an award. No, because even this evolution is not the end! This shutter was unlucky because it was created initially for a camera called the Zenit-18. Remember the story about the Zenit-16 and its vertical travel cloth shutter? This was a continuation. The new SLR was conceived as an automatic camera with aperture priority. The automatic shutter should have had electromechanical control of curtains. That’s why the promising metal blade shutter was equipped by electromagnetic curtain stoppers.
This decision in itself was not new. There were many SLRs with electromechanical control made out of the USSR. All of them were power-dependent, like the KMZ-made shutter. But of all those known at that time, it was done in the most unfortunate way. The spring tension is adjusted so that the natural mechanic speed of shutter was 1/1000. To make a slower speed, the electromagnet holds the second curtain longer. It means that without batteries or if the power supply from the battery is weak the only shutter speed available is 1/1000. The Zenit-18 was manufactured to the tune of only 7,001 copies and soon abandoned.
But there was no other shutter for Zenit-19 and it lost badly to Ukrainian counterpart Kiev-19 which needed batteries only for its light meter. In the mid 1980s, KMZ managed to accelerate this shutter up to 1/125 sync speed, but top speed of 1/1000 still remained the trademark of Soviet SLR shutters. Finally the release of Zenit-19 was discontinued by decision of the ministry, in favour of the Kiev-19.
It was considered that the reason was the intrigues of lobbyists of the Arsenal plant. But I’m sure, that it was absolutely correct decision because «ФЗЛ» shutter was an example of engineering failure. By the end of the 1980s KMZ created absolutely new metal blade shutter «ФЗЛ-84», not similar to any other design. Anatoly Padalko and Nikolay Isayev got the copyright certificate SU1278784 in December 1986.
The Copal Square won over all its Eastern Bloc counterparts because of its extremely successful design
The blades unfolded as a fan around the axis under the frame corner but the major slot-forming blade moved strongly parallel to the frame sides thanks to a simple and ingenious rocker mechanism. This shutter already had backup sync speed 1/125 without batteries. Comprehensive description was published in the Soviet Photo in February 1989. But this well-designed shutter was made too late. It used in the Pentax K-mount Zenit-AM SLR family but the sun was setting on the Soviet photo industry.
The Zenit-APK was already equipped with a Japanese Copal shutter, a batch of which was purchased for foreign currency. Soon, the place of Soviet photographic equipment on the store shelves was taken by Japanese cameras instead. The Copal Square won over all its Eastern Bloc counterparts because of its extremely successful design.
So successful, that we can afford to forget about it in the cameras we shoot, and struggle even to describe how it works.
I haven’t found Praktica L series shutters any more difficult to remove from cameras than Copal or Seiko shutters – they all require a similar amount of dismantling to reach them. The B series Praktica shutter is a development of the L series shutter. It has front and back plates like the Copal (the L series shutter uses the camera body as a back plate), but the shutter blade layout is like the L series, only inverted – the cocking latches are at the bottom of the shutter rather than the top.
Fascinating article, with insights into Eastern Bloc camera design not previously explored in such depth. Thanks very much.