Minolta Auto Semi

The Auto Semi Minolta is a Japanese 6x4.5 folding rangefinder camera, released in 1937 and available at least until 1943. It was made by Chiyoda Kōgaku (the predecessor of Minolta) and distributed by Asanuma Shōkai. It is completely different from the viewfinder Semi Minolta (I) and II, with which it only shares a few parts.

The body of the Auto Semi Minolta is largely copied from the Welta Weltur, in particular the folding struts and the focusing system are identical. The focusing is controlled by a small knob placed on the right of the folding bed, moving the whole lens and shutter assembly (unit focusing). The range- and viewfinder is contained under a top housing, whose shape is again inspired by the Weltur. Both devices are combined and share the same eyepiece at the right end of the camera. The Auto Semi Minolta was certainly the first serial-produced Japanese camera to have a combined range and viewfinder, only preceded by the Olympus Standard and perhaps the Lord prototypes.

The name Minolta is engraved between the rectangular viewfinder window and the round rangefinder window. The same Minolta engraving is present on a small black plate inside the folding bed, covering the focusing mechanism. Above the top housing there is an Auto Semi engraving, the serial number and an accessory shoe. The front leather is embossed Minolta.

The Auto Semi Minolta has an automatic film advance device inspired by Plaubel products like the Roll-Op folder or the rollfilm backs of the Makina. It is placed in a housing at the right end of the bottom plate, near the back latch. This housing supports a big advance knob and a large and thin exposure counter disc, with 1 to 16 graduations facing a red-dotted index. On the back, there is a sliding button to unlock film advance, and the same housing also supports the folding bed release. The case of the Auto Semi Minolta has a flap to cover the advance knob and exposure counter. The tripod screw is located at the opposite end of the bottom plate. The back is hinged to the left, with a red window protected by a vertically sliding cover at the top left, only used to position the film for the first exposure. The film chamber contains two pivoting cradles, one on each side, maintaining the film spools in place.

The Auto Semi Minolta somewhat evolved during its production run. The shutter was first a Compur (T, B, 1–250) then a Crown-Rapid (T, B, 1–400) in #0 size, made by Chiyoda itself. The latter is a down-sized version of the shutter made for the Auto Press Minolta. The use of an imported Compur on the early cameras perhaps indicates that the small Crown-Rapid was not yet ready for production when the camera was released. The shutter is normally not synchronized on either version, but some examples are found with a non original synch post.

The Auto Semi Minolta was produced in the Mukogawa plant, together with the other bellows models, at a rate of about 250 units per month around 1938.

The second version has a Crown shutter giving T, B, 1–400 speeds. The shutter release has moved to the top plate, above the hinge of the folding bed. The shutter is inconsistently called "Crown II", "Crown RS" (presumably for "Rapid Shutter" or Rapid with Self-timer") or "Crown Rapid II" in the original documents. It is externally a copy of the Compur-Rapid and it is probable that the mechanism is too. The speed rim is engraved CROWN–RAPID and the shutter plate is marked CROWNII–TIYOKO at the top. (Tiyoko is an alternate writing for Chiyoko, itself an abbreviation of the company name Chiyoda Kōgaku.) There is a self-timer exactly similar to the one mounted on the Compur, whose control lever is sometimes broken on the examples found today.

For the first version, examples are known with body numbers from 4039 to 4606 and lens numbers from 32889 to 34379. For the second version, the earliest examples have the same type of advance knob as on the previous version; body numbers are known from 5487 to 6447 and lens numbers from 37408 to 40598. Most cameras have a new type of advance knob with a flatter top and three grooved rows; body numbers are known from 7208 to 11592 and lens numbers from 38544 to 62865. Minor variations are known in the folding bed release button (striated or flat tip) but they perhaps occurred independently.

Inside the cameras with Crown shutter, the cradle for the supply spool is different from the corresponding part in the Compur model. It also seems that the actual size of the picture frame was slightly reduced (from 44×58mm to 43×57mm). It would be further reduced on later examples, to 42×55mm. It is possible that edge sharpness was considered insufficient and that the image size was slightly cropped as a result.

The lens is a unit-focused four-element Promar Anastigmat Nippon 75mm f/3.5 on all the cameras, the same lens as on the Minoltaflex. It was made by Asahi Kōgaku (predecessor of Pentax), which also made the three-element Coronar lens of the Semi Minolta. The aperture scale is always screwed to the bottom of the shutter plate.

Body numbers for the Auto Semi Minolta have been observed or reported from 4039 to 15069. The collected data is not homogeneous and contains some gaps, but examples are known in the 4xxx, 5xxx, 6xxx, 7xxx, 8xxx, 10xxx, 12xxx, 13xxx, 14xxx and 15xxx ranges. The sequence was certainly specific to the camera, and perhaps started at 4000. We can make a reasonable estimate for the total production at 11,000 units, in a single batch from c.4000 to c.15000, but we cannot discard the possibility that several batches were made.

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