Pentax 645

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The Pentax 645 is a medium format SLR camera, introduced at the 1984 PMA. It takes 15 pictures nominally 6x4.5 cm, on 120 roll film, or 30 on 220 film, and it can also use 70 mm film, which gives approximately 90 frames per roll. It has a built-in motor drive and a low-profile prism viewfinder with built-in dioptric correction. The camera looks somewhat like the Mamiya M645 E (but predates it by several years, and also offers more exposure options than any of the manual-focus M645 cameras).

Film is loaded onto holders (each being essentially a pair of spool holders and a pressure plate, mounted on a removable camera back plate). A holder, once loaded, is inserted into the back of the camera body and fastened in by turning a key built into the holder. Holders cannot be exchanged mid-roll.

The camera has several automatic exposure modes. Most exposure controls are accessed via menus in a liquid-crystal display (LCD) on the top, to the right of the eyepiece. The menus are operated with buttons (on the left of the VF eyepiece) to select parameters such as exposure mode, ISO speed and exposure compensation level, and up/down navigation buttons to the right of the LCD. This is very different from the controls on the Mamiya medium-format SLR cameras of the same time.

The camera requires six AA batteries, loaded in the grip on the right hand side, to power all camera functions. There is also a lithium battery fitted in the base of the camera, which serves to maintain the electronic memories. There is no battery check as such; the manual suggests that the performance of the power winder is affected by low batteries before other camera functions. If the battery becomes flat, the film can be advanced manually by removing a knob on the base of the camera with a coin and screwing into the left side body and rotate the knob clockwise. The grip is removable, but this is mostly for convenience of loading the batteries; the grip is essential for use of the camera, carrying the batteries, the main on-off switch and the shutter release button.

A limited edition Pentax 645 Japan or Pentax 645J version was released with a urushi (black, brown, gold) finish and a gold nameplate.

Contents

System

Lenses

The camera was introduced in 1984 together with seven lenses: 45mm f/2.8, 55mm f/2.8, 75mm f/2.8 and 75mm f2.8 LS (leaf shutter), 80-160mm f/4.5, 150mm F/3.5 and 300mm f/4, in addition to a 1.4X teleconverter for the 300mm lens and an adapter to use Pentax 6x7 lenses[1].

Lens Lens construction Filter diameter Overall length Diameter Minimum focusing distance Weight Introduced
SMC PENTAX-A 645 35mm F3.5 9 elements in 8 groups 77mm 67mm 80mm 0.30m 470g
SMC PENTAX-A 645 45mm F2.8 9 elements in 8 groups 67mm 66.5mm 74mm 0.45m 400g 1984
SMC PENTAX-A 645 45-85mm F4.5 11 elements in 9 groups 77mm 99mm 79mm 0.5m 805g 1996
SMC PENTAX-A 645 55mm F2.8 8 elements in 7 groups 58mm 60.5mm 74mm 0.45m 410g 1984
SMC PENTAX-A 645 75mm F2.8 6 elements in 5 groups 58mm 37.5mm 74mm 0.60m 240g 1984
SMC PENTAX 645 LS 75mm F2.8 6 elements in 5 groups 58mm 49.5mm 76mm 0.75m 365g 1984
SMC PENTAX-A 645 80-160mm F4.5 11 elements in 11 groups 77mm 131mm 82.5mm 1m 1010g 1984
SMC PENTAX-A 645 Macro 120mm F4 9 elements in 7 groups 67mm 110mm 78.5mm 0.39m 695g
SMC PENTAX 645 LS 135mm F4 5 elements in 5 groups 58mm 69mm 76mm 1.25m 470g
SMC PENTAX-A 645 150 mm F3.5 4 elements in 4 groups 58mm 71.5mm 74mm 1.4m 435g 1984
SMC PENTAX-A 645 200 mm F4.0 4 elements in 4 groups 58mm 116mm 74mm 2m 570g
SMC PENTAX-A* 645 300mm F4 ED [IF] 8 elements in 8 groups 77mm 208mm 93mm 3m 1360g 1984
SMC PENTAX-A* 645 600mm F5.6 ED [IF] 12 elements in 11 groups 49mm (drop-in) 353mm 156mm 5m 4800g


Focusing screens

  • UE-20 Plain matte
  • UG-20 Section line matte (grid)
  • UA-21 microprism matte
  • UB-21 Split image matte
  • UC-21 Split-image microprism matte

Film holders

  • 120 holder (15 exp)
  • 220 holder (30 exp)
  • 70mm holder (90 exp)


Specifications

Camera type: 6x4.5 cm SLR (actual image frame 56x41.5 mm)

Lens mount: Pentax 645 A bayonet

Standard lens: 75 mm f/2.8

Shutter:

  • Vertical-running focal-plane shutter with cloth curtains. Speeds 15 seconds - 1/1000 second, plus 'B'.
  • Camera also accepts leaf-shutter lenses.
  • Synchronised for flash via a hot shoe on top of the prism and a PC socket; X-synchronisation at 1/60 second or slower.
  • Shutter release button on grip; threaded for a cable release.
  • No delayed action.

Metering and exposure:

  • Through-the-lens, centre-weighted metering with ISO range 6-6400 in 1/3 stop increments
  • Several exposure-control modes:
    • Shutter speed priority automatic
    • Aperture priority automatic
    • Programmed automatic
    • Manual
    • TTL metered flash
    • Programmed automatic flash
    • Special mode for leaf-shutter lenses

Viewfinder:

  • Fixed low-profile prism viewfinder; telescopic eyepiece with built-in dioptric adjustment.
  • Interchangeable focusing screens; standard screen with microprism and split-prism rangefinder focusing aids.
  • LED indication of exposure settings and warnings.

Film advance:

  • Built-in power winder
  • Manual film winding knob can be attached (on the right of the body), but is recommended only as an emergency measure in the event of battery failure.

Other features:

  • ¼ inch tripod bushes on the base and on the left-hand side of the body.
  • Depth-of-field preview lever on the right of the body.


Notes

  1. Popular Photography, June 1984 p. 73

Links

Bibliography

  • Lewis, Gordon, ed. The History of the Japanese Camera. Rochester, N.Y.: George Eastman House, International Museum of Photography & Film, 1991. ISBN 0-935398-17-1 (paper), 0-935398-16-3 (hard). P.176.
  • Sugiyama, Kōichi (杉山浩一); Naoi, Hiroaki (直井浩明); Bullock, John R. The Collector's Guide to Japanese Cameras. 国産カメラ図鑑 (Kokusan kamera zukan). Tokyo: Asahi Sonorama, 1985. ISBN 4-257-03187-5. Item 2055.
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