History of Early Pentax

In the year nineteen hundred and nineteen the Asahi Optical Company Limited was formed and commenced manufacturing spectacle lenses. The name 'Asahi' which, incidentally, means 'Rising Sun' was selected as a characteristic symbol of hope and promise ‑ a promise that over the years has been fully achieved.

In the year 1923 Asahi added to their production programme, lenses for cine-projectors, and certain other optical components, which continued up to 1931 when the first camera lenses were manufactured.

1948 saw the first prism binocular production, which was followed later by equally high grade telescopes, soon to become deservedly world renowned.

The year 1951 was later to prove of paramount importance in that Asahi manufactured the Asahiflex I, the first 35 mm SLR camera to be made in Japan. Further intensive development continued, but it was not until 1954 that what may be regarded as a somewhat revolutionary development in SLR camera design was announced ‑ the instant return mirror, allowing uninterrupted screen viewing.

In 1955 the Asahiflex II a was introduced, differing only from the II b in that it had positioned on the front of the camera a separate dial for the slow shutter speeds. Two years later the name Pentax appeared when the first Asahi Pentax camera was introduced, and it was at this stage that the new eye‑level Pentaprism finder was incorporated. Indeed, this model of the new Asahi Pentax set the basic design and shape of the latest models that we know today.

1960 will undoubtedly be remembered as a year of very real significance when Asahi perfected a through‑the‑lens metering system, which was eventually incorporated in the 1964 model and named the Asahi Pentax Spotmatic. Later developments include a motor drive unit and many accessories, both simple and complex. It may be of interest to many and perhaps a surprise to some, to learn of the true derivation of the Asahi Pentax name 'Spotmatic'. When the prototype Spotmatic camera was introduced for the first time at Photokina in Cologne way back in 1960 the metering device was, quite literally, designed for use as a Spot Meter measuring a restricted area of the subject only. However, after intensive discussions and considerable testing in laboratory and field, the Asahi technicians finally decided ‑ albeit with some regret ‑ that the employment of the 'Spot' system would be too complex for the average user, from the actual operating point of view, and, to a lesser degree, the time factor involved.

Consequently, the averaging method employed in the Spotmatic, as it is known today, was finally decided upon. Generally speaking, it was felt that this would help the user to achieve more consistent overall results.

Nevertheless, that very first appearance of the Asahi Pentax Spotmatic prototype, having caused such considerable and widespread interest (indeed, it was one of the major topics of conversation at the Fair) finally influenced Asahi to retain a name which was already becoming symbolic of a new evolutionary concept of the 35 mm SLR camera with one of the world's first through‑the‑lens metering systems. (Another world's first ‑ the now historic instant‑return mirror, had already been evolved in the year 1954).

As enthusiasts know, the Spot metering system is now available in the shape of a highly sensitive and accurate accessory (Asahi Pentax Spot-meter Mk. III). So, through the undoubted wisdom and now, correctly adjudged, foresight of the manufacturers, virtually the best of both worlds is available.

The underlying policy of the Asahi Optical Company is essentially one of evolution. This is not in any way to be confused with the present day tendency of some manufacturers to produce a 'new' model once or twice a year purely for sales and publicity purposes, be it cars, refrigerators, or cameras.

Their sincere belief is that if through experience gained over the years even one single operation can be made easier, one component more efficient, or by the introduction of completely new thinking and applied technology, the advancement of a whole new system, then no effort should be spared in order to ensure the successful incorporation of results into new and existing equipment.

Not only does this development programme depend on the successful presentation of new ideas, but also the ability to transmit such ideas from paper to machine stage. It is here that Asahi's constant expansion and the subsequent availability of sophisticated electronic equipment and computers has enabled them to become leaders in the development, production, and sales of cameras, lenses, and accessories.

Thus it will be seen that Asahi Optical Co. have been lens manufacturers from the very beginning of the formation of their Company which must, inevitably, provide a unique background of specialist knowledge, later broadened with their introduction of binocular and camera design which, undoubtedly, will account for the superb quality of their products today. This has permitted the rigid quality control of every stage of operation in the design and manufacture of lenses and equipment undertaken within the Asahi plants.

Asahiflex 1 (1951)
This conventional style 35 mm Single Lens Reflex camera was the first of its kind to be manufactured by the Asahi Optical Company. A somewhat. complex focal plane shutter provided a speed range of 1/25 to 1/500 see. and provision for X Flash synchronization.
Focusing and viewing was by means of a waist-level Finder Screen. An Optical Viewfinder was incorporated, sited next to the Viewfinder Screen. The standard optical equipment was a 50mm 3.5 Takumar lens with preset diaphragm. Altogether six interchangeable lenses were introduced ranging from 50mm (standard) - 50O mm (long focus). It should be noted that the lenses manufactured at this time and, indeed, those made for the three subsequent models were supplied in different lens mounts to the lenses designed and manufactured for all later Asahi 35 mm SLR cameras bearing the name Pentax. These early pattern lenses can be used on Pentax model camera bodies by the use of a special lens mount adapter. However, it is not possible to use Pentax series lenses on the early original models described above.

Specification
35 mm Single Lens Reflex Camera 24 X 36 mm.
Waist-level reflex focusing. Eye level optical viewfinder.
Focal plane shutter.
Speed range: 1/25 - 1/500 sec. X Flash synchronization.
Standard (non-return) reflex mirror. Film transport knob.
Film exposure counter dial.
Lens mount: original pattern thread. Standard lens: 5O mm f 3.5 Takumar (preset diaphragm).
Interchangeable Lenses: Six. 5O mm - 50O mm.
Satin chrome trim.

Asahi Pentax (1957) (Original)

The evolution of the Asahi SLR camera range was far more pronounced in this new model than at any previous stage and indeed the designation Pentax refers to a completely new body design with many important and major features. First, the new body housed the all important built-in, eye-level viewing and focusing Pentaprism, beneath the top cover. Second. a new lens mount designed to accommodate a larger thread. Other new features included a rapid wind lever wind and a folding rewind crank. The shutter speeds again controlled by two separate speed dials ranged from 1 sec. - 1/500 sec. and B & T. Flash sockets were provided for both FP and X synchronization. Incorporated in the eye-level Pentaprism viewfinder and focusing screen was a Fresnel lens. The Prism assembly provided a life size image when using the standard 58 mm lens. Initially a 5O mm f 3.5 lens was offered as the basic standard optic, but, soon after, wider aperture lenses became more freely available, the user being able to select from a choice of three. Therefore, apart from the 5O mm f 3.5 there was the optional choice of 58 mm f 2 Takumar, 55 mm f 2.2 Takumar, or the 58 mm f 2.4 Takumar. All three lenses had preset diaphragms.

Specification
35 mm Single Lens Reflex Camera. 24 x 36 mm.
Permanently housed eye-level Pentaprism finder incorporating Fresnel lens for focusing.
Focal plane shutter.
Speed range: 1 - 1/500 sec. T & B. (two shutter speed dials).
X & FP Flash synchronization.
Instant return reflex mirror.
Film transport rapid wind lever. Film rewind folding crank.
Film exposure counter dial (additive).
Lens mount (new, with larger threads).
Standard lenses: 55 mm f 2.2 Takumar. 58 mm f 2.4 Takumar. 58 mm f 2 Takumar. All preset diaphragms.
New camera body.
Satin chrome trim.

Asahi Pentax S3 (1960)

Again comparatively minor modifications concerning the camera body but with the introduction of the first of the Super-Takumar lenses equipped with fully automatic iris diaphragm control, thus eliminating the manual presetting of the diaphragm as was necessary with the earlier type semi-automatic lens mechanism. This all important evolution in design meant even simpler and faster operation allowing complete concentration on vital matters concerning viewing/focusing etc. The standard lens was, in fact, a 55 mm f 1.8 Super-Takumar which, as stated above, was fully automatic, although it is worth noting that a small number of early pattern lenses of this specification were designated 'Auto-Takumar' albeit that these lenses were, in fact, identical to the fully automatic Super-Takumar. Improvements were also made in the Fresnel lens of the Pentaprism and a new top shutter speed of 1/1000 sec. Again a full black trim body version available as optional choice from standard satin chrome.

Specification

35 mm Single Lens Reflex Camera 24 x 36 mm.
Permanently housed eye-level Pentaprism finder incorporating a central Micro-prism focusing grid in centre of Fresnel lens.
Focal plane shutter.
Speed range: 1 - 1 /1000 sec. and T & B.
X & FP synchronization.
Instant return reflex mirror.
Film transport single stroke rapid wind lever.
Film rewind crank.
Film exposure counter dial.
Film type indicator dial.
Current lens mount.
Standard lenses: 55 mm f 1.8 Takumar (fully automatic).
Red dot shutter 'cocking' indicator.
Standard satin chrome trim or full black version.

Asahi Pentax Spotmatic (1964)

Type
35mm Single lens reflex camera, with built-in through-the-lens Exposure Meter.
Film and picture size
35mm film (20 or 36 exposures) 24 x 36mm.
Finder
Permanently housed eye-level Pentaprism finder incorporating a central Micro prism focusing grid in centre of Fresnel lens.
0.88x magnification with 5Omm lens. Approx. life size with 55mm lens.
Shutter
Focal plane shutter with single non rotating dial, speeds 1 sec. - 1/1000 sec. and incorporated self-timer with variable 5-13 sec. delay. Shutter blinds of special rubberized silk.
Flash Synchronization
Synchronized for FP & X. Electronic at 1/60 sec.
Reflex mirror
Instant return mirror with special shock absorbers for minimum vibration.
Film transport
Ratchet type rapid wind lever (for film advance and shutter cocking).
10 degrees pre-advance and 160degrees advancing angle.
Shutter 'cocking' indicator
When 'cocked' a red disc appears alongside the shutter release button, and blacks out when released.
Film exposure counter
Automatic reset type. Exposure counter automatically resets to -2 when back is opened.

Film rewind
Rapid rewind crank for fast film take-up.
Film type reminder dial
Film type indicator under rewind knob with ASA rating window.
Accessory clip
Grooves located on either side of the viewfinder window frame. Accepts 90' finder, magnifier and other accessories.
Lens mount
42mm threaded lens mount.
Dimensions
Width 143mm: height 92mm: depth 88mm with standard 5Omm fl.4 lens.
Width 143mm: height 92mm: depth 87mm with standard 55mm fl.8 lens.
Weight
Body only: 621 g. With 5Omm lens: 851 g. With 55mm lens: 836g.
Standard lenses
50mm fl.4 Super-Takumar. 55mm fl.8 Super-Takumar. with fully automatic diaphragm. Filter and lens hood size: 49mm. Equipped with diaphragm preview lever affording visual check of depth of field.
Distance scale: 45cm - infinity.
Finish
Satin chrome or black trim.
Exposure meter
Built-in. Measures brightness of the ground glass and is coupled directly to shutter and film speed settings.
Film speed ASA setting ranges from 20-1600 (LV 1 - 18 for ASA 100 film with standard lens).
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Asahi Pentax SL

The Asahi Pentax SL is identical to the Spotmatic. It accepts the same super Takumar interchangeable lenses and accessories. It has the same brilliant micro-prism focusing system. In fact, just check these features Identical high precision shutter Identical instant return mirror. Identical automatic diaphragm mechanism. Identical rapid wind-lever for film transport/s h utter cocking. Identical auto-reset film counter. Identical flash synchronization (incorporating white gold contacts for maximum efficiency).
Identical durability and reliability to meet exacting professional standards.
Identical mechanical and optical quality, and the same easy method of operation.
Compact, lightweight (even lighter than the Spotmatic) and it handles superbly.
Lighter than the Spotmatic? Yes, due to the fact that the Asahi Pentax SL has no built-in exposure meter, which reduces not only the weight, but the cost. However, the Asahi Pentax clip-on Meter (model SL) can be instantly fitted to the SL shutter speed dial. Therefore, everything that has gone into the making of the Asahi Pentax Spotmatic is contained in this fine instrument and it is eminently suited for those with tight budget schedules or specialist workers preferring to rely on Spot meter III accessory, where the highest possible degree of accuracy is called for. Other users requiring additional camera bodies as a convenient means of carrying a readily available choice of film emulsion, i.e. high speed / low speed / monochrome / colour or negative / reversal colour, will doubtless welcome the introduction of SL, for obvious reasons.

Asahi Pentax ES

The Pentax ES provides a complete new phase in photography. The truth is that many professional photographers or even advanced amateurs who really know their equipment have, understandably, felt reluctant in the past to show interest in any previous form of automatic exposure system.
Indeed, those whose professional skills are so categorized, understandably wish to be in complete control of the system and all ensuing points relating, up to, and culminating in the final exposure. The Pentax ES can truly be said to offer the 'best of both worlds', the significance being in the distinct choice that is available, i.e. fully automatic exposure by means of the electronically controlled shutter, in conjunction with lens aperture pre-selection and manual over-ride, or the utilization of the mechanical or manually operated shutter speeds.
First then, let us discuss and examine the essential differences between the Asahi Pentax ES and Pentax Spotmatic II. At first glance there appear few external changes. The word 'Spotmatic' no longer appears on the front face of the camera beneath the shutter speed dial instead, a bold and slightly stylized symbol consisting of the letters ES (Electronic Shutter). The delayed action mechanism has been eliminated, and the space on the front face of the camera utilized as a recessed housing for the six-volt battery required to power both the electronic shutter and TTL exposure meter mechanism. Further scrutiny reveals a marginally deeper base plate, space having been cleverly provided to incorporate the complex electronic circuitry. This has increased the overall height by just 3mm to a total of 98mm. This, and other minor changes have also led to a weight increase of 60grams.
On turning the camera around and observing the top plate carrying the major control assembly, further changes will be noted. The shutter speed dial now has engraved in white the speeds: 1/1000 - 1/500 - 1/250 - 1/125 - 1/60 second and 'B' (Brief Time). There is also the word 'Automatic' and beside it a wedge shaped indicator. The dial locates with a positive 'click' when rotated for selection of the required setting.
A further minor change can be noticed (or felt) at the end of the film transport lever where the grooving is slightly smoother, although still affording adequate 'feel' and location for the thumb.
The viewfinder and focusing screen is basically unchanged, employing in fact the same optical system as on the previous model. However, there is now incorporated to the right of the focusing screen a vertical scale reading 1/1000 - 1 second. The scale is fractionally outside the actual critical picture viewing/taking area, and is extremely legible. Another rather unique feature is that the scale remains brilliant and easy to read, under virtually any normal lighting conditions.
The film rewind crank assembly has been redesigned, and apart from providing index settings on the surrounding milled discs for film data information (both film 'type' and 'speed') there is also a completely new control known as the Exposure Factor Control Dial. Its purpose is to allow intentional over / under exposure whilst the camera is being employed with the fully automatic control setting. This override control may be required for several reasons, e.g. when exposing against the light, or when photographing a relatively small illuminated subject against a large dark background.
Once the necessary over-ride setting has been made, the fully automatic shutter of the ES compensates accordingly.
The film type reminder index is also quite new. This consists of a pair of small protruding pointers on the outer edge of a disc located beneath the rewind knob. It is set by gently pulling out the rewind knob and rotating the selector dial to the appropriate symbol, i.e. Daylight, Tungsten, Colour, Black & White, or Empty. The film speeds incorporated range from ASA 20-1600, and are set by lifting, rotating and lowering the milled disc surrounding the rewind crank. Manual over-ride of the automatic exposure control is also operated by turning the upper milled disc bearing settings ranging from 0.5x, lx, 2x and 4x (for normal operation the dial is left at the 1x position).
There is a broader and new type knurling forming the focusing grip around the lens barrel, which appears to be a slightly soft synthetic material providing a more positive 'feel', especially when working out of doors or with cold fingers. Very noticeable is the constant striving on the part of the manufacturers to produce the finest possible instrument, which is seen with regard to these comparatively trivial changes, i.e. the thumb grip on the film transport lever and the lens knurling, trivial, perhaps, in themselves, but so important collectively.
As mentioned earlier, the delayed action mechanism has now been abandoned and the space utilized to provide a housing for the silver oxide type battery (used for powering both shutter and TTL exposure meter). The battery used is a 6 volt Ever Ready No. 544 or Mallory 4G1 3. Naturally, the cell must never be allowed to drop beneath a minimum specified power, and so a test button is provided to the right of the rewind assembly which when depressed will cause a deflection of the meter needle to within a specified segmented area of the scale (opposite the figure 30). If the needle fails to reach the specified area then replacement of the cell is essential and it is for this reason that users of the Pentax ES will normally wish to carry a spare.
Incidentally, if the shutter is fired and an exposure made with the shutter speed set on the 'automatic' position with an 'exhausted' battery, the shutter will work at 1/1000 second.
It should be emphasized, however, that the Pentax ES does virtually offer the 'best of both worlds' allowing normal manual operation of the mechanical shutter speeds as and when required.

'Memory' device': Electronic exposure control in one form or another is not new and indeed has been used in certain cameras for a number of years. However, Asahi Pentax ES represents a 'world's first' in relation to the introduction of electronic exposure control used in conjunction with TTL metering incorporated in a 35mrn SLR camera.
Certainly without the 'Memory' device the system just could not function, and it is to Asahi's very real credit that a means has been found to overcome what seemed until recently a seemingly insuperable problem. In brief, the problem was caused by the obstruction of the light path through the lens immediately prior to the opening of the shutter, due to the lifting of the reflex mirror assembly. With the ES system any fluctuation of light is 1 noted' from the moment the shutter release is partially depressed (at which time the meter is switched on) up to the moment the shutter is released, when the reading is 'locked'. This is achieved by means of an electromagnet energized by the current flowing through and from the photo resistive elements of the CdS meter.
The result is that according to the light intensity, governing in turn the strength of current flowing through the magnet, so is determined the actual position of the core of the magnet at that precise moment. This in turn controls the slit width of the focal plane shutter blind which governs the exact shutter speed.
Therefore, although the meter is virtually 'inoperable' during that brief period when, as mentioned above, the light rays are obscured from the CdS cells by the lifting of the reflex mirror assembly the focal plane shutter has been programmed, preset as it were - ready for the correct exposure to be made.
A further and obvious advantage is that the system permits an infinitely variable range of shutter speeds ensuring very accurate exposure. The 'memory' device regulates the light intensity up to the moment the exposure is made. It may result in a shutter speed of 1/727 or 1/13 second, but whatever the actual speed it will be correct.