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The History of the 35mm SLR Camera

Design Innovations



The Early Years


1936 - The first consumer 35mm SLR - the Kine Exakta - was made by the German Ihagee Company. It had a waist-level finder, and was essentially a scaled-down version of a roll-film camera design. It had a focal-plane shutter and removable lens.

1948 - German supremo Zeiss had started work on a 35mm SLR in the 1930s, but WWII delayed progress allowing the Italian Rectaflex to come to market the year before the post-war, East German Contax S. Both models established the blue-print for all subsequent 35mm SLRs; a pentaprism which allowed eye-level-viewing of an image oriented correctly from left to right, a removable lens, and a focal-plane shutter ... which would take some years to become the dominant shutter option.

To sum-up the early years - all that really happened was the 35mm SLR established an identity.


The 1950s


1953 - The East German Contax E was the first 35mm SLR with a built-in light meter, but this was an uncoupled, external selenium cell (mounted behind a door on the pentaprism housing). Meanwhile, in the West, the Zeiss Ikon factory introduced the Contaflex I: the first leaf shutter 35mm SLR.

1954 - The Japanese Asahi Optical Corporation (which was to become Asahi Pentax) launched the Asahiflex IIB (Sears Tower 23 in the USA): the first 35mm SLR with a reliable instant return mirror. Before this innovation, viewfinders went black after an exposure, and the film would have to be wound to re-set the mirror and restore visibility.

1956 - A number of manufacturers independently developed and adopted external mechanisms to automate closure of the lens diaphragm (stop-down) immediately prior to exposure. This prevented the viewfinder from becoming too dim for the image to be seen clearly, once a small aperture had been set in preparation for an exposure. The Japanese Miranda T used a 'Pressure Automatic Diaphragm' (PAD), where pressing the release button on a lens arm closed down the diaphragm, and then further pressure pushed the camera shutter release. A similar mechanism was used on the East German Exakta Varex IIa, but the Praktica FX2 took a different approach and introduced a lens based semi-automatic diaphragm pre-setting dial (i.e. a lens housed dial to close the aperture to a pre-set f-stop).

1957 - The Asahi Pentax (Sears Tower 26 in the USA) established the modern 35mm SLR control layout; a right-handed rapid-wind thumb lever, a fold-out film rewind crank, and a microprism focusing aid.

1958 - The Japanese Zunow Optical Industry's Zunow had the first fully automatic internal mechanism that coupled the lens diaphragm to the shutter release, so that the lens iris closed (stopped-down) prior to the moment of exposure.

1958 - The West German Carl Braun Paxette Reflex (a leaf shutter SLR) had an external, top mounted, coupled light meter needle system.

1959 - The Zeiss Ikon Contarex (known as the Bullseye or Cyclops) was the first focal-plane SLR with a built-in light meter coupled to a viewfinder centre-the-needle needle pointer. The pointer showed the counterpart aperture for the selected shutter speed.

1959 - The French Royer Savoyflex Automatic was the first 35mm SLR to offer shutter priority automatic exposure, controlled by a Selenium meter on the outer face of the prism housing. The camera used a leaf shutter.

To sum-up the 1950s - the inconveniences of an SLR were ironed-out in this decade; darkened views prior to exposure, followed by complete black-out. Metering systems were still in their infancy, and those that existed were not bespoke to the SLR. However, in 1959, the Japanese company Nikon introduced their first camera in this class, and it was a total show-stopper. The Nikon F was a professional calibre 35mm system SLR, with a focal-plane shutter, instant return mirror, pentaprism and auto-diaphragm design, along with excellent interchangeable lenses and a huge accessory system ... such as an add-on motor drive. The F itself was not technologically ground-breaking, but its impact established the 35mm SLR as the dominant professional system, displacing the 35mm Range Finder, and ending the popularity of the medium format twin-lens reflex (TLR). More than that, the camera established Japanese manufactures as the new leaders in camera design and manufacturing.



The 1960s


1960 - The Konica F was the first SLR with a focal-plane shutter speed of 1/2000th (and 1/125th flash X-synchronisation). Focal-plane shutters comprise two curtains, and their x-synchronisation speed (X speed) is the amount of time for which both curtains are fully open. The curtains do not move faster than their X speed. Quicker exposure times are achieved by timing the second shutter curtain to close sooner after the first curtain opens, such that the opening between them narrows, and a moving slit travels across the film. It had not previously proved possible to exceed a speed of 1/1000th (and a typical X speed of 1/60th), because the curtains proved too fragile to survive the necessary accelerative shocks. Konica's innovation was to design a new shutter which changed the curtains direction of travel from horizontal to vertical, which resulted in a shorter distance to be traversed - making faster exposure times possible. The cloth curtains were additionally replaced by metal blades. This type of shutter had certain vulnerabilities, and was not universally adopted until further developments ironed-out its wrinkles (but it got there in the form of the Copal Square).

1963 - The Kowa H was the first SLR equipped with a selenium photocell on the front of the prism housing, which controls both the shutter speed and aperture size according to a predetermined program curve. The exposure could also be set manually.

1963 - The Topcon RE Super (called the Super D in the USA) was the first SLR with through-the-lens (TTL) light metering. This was a great leap forward. Previously, light meters were either separate handheld devices, or some cameras had integral meters with a light cell somewhere on the exterior of the camera body. The disadvantage either posed was the luminescence they measured was not exactly the same as that which passed through the camera's lens. The RE Super had an internal cadmium sulphide (CdS) photo-resistive cell mounted behind non-silvered slits in the reflex mirror, providing through-the-lens, full area averaging metering. Like the Cyclops, the aperture and shutter settings were coupled to the meter, so exposure requirements could be monitored through a viewfinder centre-the-needle system. In addition, the Topcon metered with the lens aperture fully open, at its widest setting.
TTL metering became normal in virtually all 35mm SLRs by the late 1960s. The 1965 Nikon Nikkormat FT, and 1966 Minolta SRT101 had open aperture metering, however, many others lagged behind. The 1964 Asahi Pentax Spotmatic offered coupled, viewfinder centre-the-needle, TTL metering, but it worked by stopping-down the lens diaphragm to take a reading. The Spotmatic adopted two CdS cells on either side of the eyepiece, because reading off the focusing screen was less expensive and less complex than the RE Super's system, and this easier solution proved more popular (in the short term).

1964 - Topcon introduced their second innovative camera - the Topcon Uni - which was also sold as the Beseler Topcon Auto 100, and Hanimex Topcon RE Auto. This was the first SLR with automatic exposure TTL metering. A viewfinder needle points to the aperture the camera will set for any selected shutter speed when in auto mode, or the aperture that the user should select when in manual mode.
The Uni's features were not significantly copied, probably because it broke-step with trends in SLR design by using a leaf shutter, but it did set other manufacturers on a path to automate a component of exposure setting. The first automated exposure systems were in fact 'semi-automatic', since the user had to set one variable in order for the camera to automatically generate a counterpart value.

The Soviet Union KMZ company interrupted Japan's emerging dominance of the industry by producing the Zenit 5. This was the first SLR with built-in electric motor drive for automatic single-frame film advancement.
Built-in motor drives did not become common in 35mm SLRs until the early 1980s, when small and efficient micro-motors were perfected. However, add-on auto-winders were very popular in the 1970s.

The USA/West German Kodak collaboration produced the Kodak Retina Reflex IV. This was the first SLR to have an ISO (International Organization for Standardization) hot shoe for direct flash mounting and synchronization. The Kodak was not the first camera with a hot shoe connector: the Univex Mercury, non-SLR, half frame 35mm did that in 1938. Although the Nikon F had a hot shoe, it was non-ISO. The ISO hot shoe became a standard SLR feature in the early 1970s.

1966 - The East German manufacturer Pentacon produced the Praktica PL Electronic; the first SLR with an electronically controlled shutter, instead of clockwork springs, gears and levers. I can find very little information on this camera (maybe it never went into production?), and whilst the technology glimpsed the future, it's difficult to judge how much Pentacon's innovation shaped things to come.

Meanwhile, the Konica AutoReflex (Autorex in Japan) became the first 35mm SLR to offer auto-exposure with a focal-plane shutter. There is some disagreement as to whether this camera was introduced in 1965 or 1966, but I've gone for the latter. The camera used a mechanical 'trap-needle' controlled by an external CdS meter that read light directly (it was not through-the-lens metering). While auto-exposure was not new, the camera nevertheless marked a step on the way to further refinement of auto-exposure in a focal-plane shutter SLR.

1968 - Konica introduced the Konica Autoreflex T and A, which was the focal-plane shutter SLR with open aperture TTL metering and shutter priority auto-exposure. To be clear, the Konica Autoreflex T replicated what the Topcon Uni had accomplished four years earlier, but using a focal-plane rather than a leaf shutter.

Mamiya launched their DTL series cameras - the Mamiya DTL 500 & 1000. These had switchable metering patterns; average and spot, for stop-down metering. There were a few manufacturers that adopted dual metering patterns (such as the 1969 Topcon Unirex - which was possibly the first SLR with open aperture dual metering, the 1970 Ricoh TLS 401, and the 1971 Miranda Auto Sensorex EE), but for some reason, switchable metering options did not catch-on, and largely disappeared until the mid 1980s, when metering options became popular.

1969 - The Yashica TL Electro X was the first SLR with viewfinder electronic lights for exposure information (miniature lamps), and also the first with an electronically timed mechanical Copal shutter with step-less speeds operating at any intermediate between 2 seconds and 1/1000th. Speeds above 1/30th are click stopped, but it is possible to set the speed dial between settings. The slower speeds are not click-stopped, reflecting Yashica's intention for lower light exposures to be metered by adjustment of the shutter speed rather than the lens aperture. The camera still relied on stop-down metering, but the ethos at work here was to use electronics to eliminate mechanical component failure.

To sum-up the 1960s - despite some manufacturers advancing technology, and numerous others embracing their new ideas, by the end of the decade, the significant change in camera design was the mainstream adoption of viewfinder centre-the-needle, or match-needle TTL metering (albeit commonly stop-down). I guess it's fair to say that the state-of-the-art camera at the beginning of the 1970s was still the Nikon F, which had been evolving and incorporating technology improvements to become the TTL metering Nikon F Photomic FTn. Braun and Exakta (to name those previously cited as innovators) where just two of several German manufactures who were unable to keep-up with the pace of change, and folded.


The 1970s

1971 - The Asahi Pentax Electro Spotmatic (ES) was the first SLR to combine aperture priority auto-exposure with an electronically controlled step-less focal plane shutter (open aperture metering). The addition of aperture priority to pre-existing shutter priority automatic exposure effectively ended the German camera industry (in the booming SLR sector), as they failed to keep up with their Japanese counterparts.

Mamiya continued to innovate and the Mamiya Auto XTL featured the first auto-exposure lock; a device that allowed re-framing after an exposure value has been set by the metering system, to used in tricky lighting situations. Mamiya called this an 'exposure hold', but it soon became a essential addition to auto-exposure cameras (e.g. the Nikkormat EL of the following year), and was more commonly known as an exposure lock, AE lock, or exposure memory lock.

Not yet defeated, Pentacon introduced the first interchangeable lens camera with an electric contact lens mount in the shape of the Praktica LLC. Their M42 screw mount had proved very popular. Over something-like 20 years it had been used by almost two dozen different SLR brands - most notably Asahi Pentax. However, by the early 1970s, the M42's limitations, especially it's lack of provision for auto-diaphragm, open aperture viewing and metering, were becoming serious liabilities. This new take on lens coupling glimpsed the future, but it didn't really lead to anything. The first all-electronic contact camera lens mount - the Canon EF mount - was adopted in 1987, when electronic autofocus required additional data exchange between camera and lens.

Meanwhile, Fuji's Fujica ST701 was the first with silicon photodiode light meter sensors. Previously, SLR TTL meters used cadmium sulphide (CdS) cells, however, CdS needed fairly bright light and suffered from a 'memory' effect where it might take several seconds to respond to a significant light level change. Although silicon's infra red response required blue filtration to match the eye's spectral response, silicon supplanted CdS by the late 1970s, because of its greater sensitivity and instantaneous response.

1972 - Fuji took Yashica's earlier work on electronics further, and introduced the Fujica ST801: the first SLR with viewfinder light emitting diodes. These soon replaced mechanical needle pointers, and became the core of increasingly sophisticated viewfinder information displays. This camera had a secondary, and often overlooked innovation; it used a horizontally travelling cloth focal-plane shutter that had a top speed of 1/2000th, which seems to be attributable to the use of self-lubricating Teflon.

1974 - Fuji were at it again, and launched the Fujica ST901: the first SLR with a viewfinder calculator-style digital LED display. Although LEDs would be succeeded by more energy efficient and informative LCDs in the 1980s, the use of electronic displays had begun.

1975 - The Olympus OM-2 was the first SLR with TTL, off-the-film (OTF) flash auto exposure. This had two rearward-facing silicon photodiodes in the mirror box, which metered light reflecting off the film. Circuitry detected when sufficient exposure had been achieved to quench the (dedicated) flash light. TTL auto-flash metering became standard in virtually all SLRs by the mid-1980s.

1976 - Canon stepped into the spotlight with the Canon AE-1: the first SLR with microprocessor electronics used to deliver shutter-priority auto-exposure. As importantly, the model introduced the use of a significant amount of structural plastic for a lighter and cheaper camera at the expense of being less impact resistance. in the same year, the Asahi Pentax ME was the first auto-exposure-only SLR. These cameras marked a shift in design goals; they were made to have relatively straightforward controls and automation that appealed to newcomers. The target market for SLR cameras was being widened.

1977 - Until now, auto-exposure SLR brands had aligned with one of two camps; shutter-priority was offered by Canons, Konicas, Mirandas, Petris, Ricohs and Topcons, while aperture-priority came from Asahi Pentaxes, Chinons, Cosinas, Fujicas, Minoltas, Nikkormats and Yashicas. While each championed the superiority of their system, the reality was based on the limitations of the electronics of the time, and the ease of adapting each brand's older mechanical designs to automation. Minolta released their Minolta XD7 (XD11 or XD elsewhere): the first dual mode auto-exposure SLR, with both aperture-priority and shutter-priority auto-exposure.

1978 - The Canon A-1 went a step further than the Minolta XD7 by offering an electronically controlled programmed auto-exposure mode. Instead of the photographer picking a shutter speed to freeze or blur motion and choosing a lens aperture f-stop to control depth of field, the A-1 had a microprocessor computer programmed to automatically select a compromise exposure from light meter input. Virtually all cameras had some sort of program mode or modes by the mid-1980s.

1979 - The Konica FS-1 was the first SLR with built-in motorized auto-loading, and auto-winding (single frame or continuous shooting up to 1.5 frames per second). It didn't have auto-rewind: that was yet to come.

Meanwhile the Pentax ME Super was the first SLR with electronic push button controls (although these were only used to alter the shutter speed). The use of push button controls multiplied, and they replaced dials switches in most 35mm SLRs by the late 1980s.

Contax/Yashica launched the Contax 139Q, where the 'Q' indicated quartz-timing. This brought the latest clock and watch technology to photography to make shutter timings very precise.

To sum up the 1970s - by the end of the decade, many cameras incorporated all of the innovations of the 1960s, plus a number of their own decade. A typical camera now had open-aperture TTL metering, plus some form of auto-exposure, along with a hot shoe, motor drive connectivity and LED viewfinder information. Towards the end of the period, the larger, heavier and mechanical systems had begun to give way to smaller, lightweight, plastic construction, and battery dependant electronics, thanks to the hugely successful Canon AE-1 and its mimics. Despite the changing cast of innovative manufacturers, Nikon were possibly still top of the pile with their F2. Despite not being the first to develop any performance enhancement, they always managed to keep pace with changes. During the 1970s, Kowa, Miranda, Petri and Topcon succumbed to increasing pressure to keep pace with innovations, and ceased camera manufacturing.



The 1980s

In a nutshell, the 1980s produced LCD data displays, new metering patterns such as Nikon's multi-segmented (matrix or evaluative) metering, where a built-in computer system analysed light levels in five different segments of the field of view, and Olympus's multiple spot-meter, which could measure eight individual spots and average them, plus the big innovation - the one that brought something completely new - auto-focus. In the 1980s, Fujica, Konica, and Mamiya were lost, although Fuji resurface when the next generation of cameras emerged.



The 1990s

In the 1990s, digital cameras became a reality ... and by the end of the decade they had killed the 35mm film SLR market. The 90s closed-down Ricoh, and Yashica, while Contax, Cosina, Minolta, Praktica and Zenit lingered into the new millennium before throwing-in the towel.



I lost interest in cameras by the early 80s. I felt automation had gone too far, and the equipment was making decisions that properly resided with the photographer. I did have a flirtation with an 80s Contax 167MT, which was seriously capable, but deciding which of its exposure modes to use (standard programmed auto exposure, programmed high-speed auto exposure, programmed low-speed auto exposure, shutter-priority auto exposure, aperture-priority auto exposure, or manual) felt laborious. I also had a 90s auto-focus Pentax MZ-5n, which I never liked, and a 'naughties' Minolta Dynax 5 (one of the last 35mm SLRs), which was awesome, but the day-to-day immediacy, simplicity, convenience, and low cost of digital finally seduced me.


Other pages at Camera Portraits

The History of the 35mm Folding Camera

The History of the 35mm Rangefinder Camera

The History of the 35mm TLR Camera

The History of the 35mm Viewfinder Camera