Pentax User Archive: Pentax release KM, KX and K2

We take a look at the Pentax KM, KX and K2 release from Volume 2, Number 1

20/04/2011 - 15:40


New Pentaxes KM, KX and K2

It is in the nature of progress that it cannot stand still. This explains why Asahi Optical Company, having developed the most popular screw-thread SLR cameras in the world, have now introduced three new models with bayonet-mount lenses. To answer what will certainly be your first question: No, existing cameras and lenses are not obsolete. Second: existing SMC Takumars arnd Super-Takumars can be used on the new models by means of a simple K adapter. Third: SMC Takumars will continue to be made for the screw-thread models.

Similar to the Spotmatic F, with the same meter sensitivity of LV3-18, and a photoswitch turning on the current when EV2-3 is reached. Metering is of the whole screen, there's a depth-of-field preview button above the self-timer, an X-synchro hot-shoe plus X and FP coaxial sockets, and ASA settings 20-3200. The mechanical stepped shutter speeds are 1-1/1000 sec plus B, cross-couple with the lens apertures to centre the needle visible in the view-finder.

The Pentax KM is slightly smaller than the Spotmatic F and the chamfered edges along the front of the baseplate make it easier than ever before to 'just hold a Pentax'.

Similar to the KM but with some sophisticated extras, including fill shutter speed and aperture readout visible in the viewfinder. When the shutter speed knob is turned a green bar indicates the sped on the viewfinder scale. As the aperture ring is turned the aperture is shown in a window along the top edge of the screen. You can see the small window providing illumination for these scales at the front of the pentaprism housing.

Metering is 70% centre-weighted, based on a highly rational current saving/readiness principle. There's no photoswitch. Pull out the wind-on lever 20% and the current passes to the meter. Take the first pressure on the button and the meter reads. Simply preparing to take a picture activates the meter. Push in the wind-on lever or lock the release button, and there is no current flow to the meter.

For convenience, the battery check button bypasses the switching procedure. The check is simple – if the needle falls below 125 the battery is still active.

For quick response in dim or changing light, the Pentax KX use fast-response Silicon Photo Diode metering instead of conventional CdS cells. Meter range is EV1-18 with 100 ASA, and the ASA scale round the rewind knob covers 8-6400. A depth-of-field preview button is handily situated above the self-timer (just where the second finger rests) and there is an X-synchro hit-shoe as well as X and FP coaxial sockets.

The KX has mirror lock-up for vibration free tripod exposures, simply ny turning a collar round the depth-of-field button, and pressing it. As with the KM, the Pentax KX is slightly smaller than the Spotmatic F, and with a smooth chamfered edge to the baseplate.

There's hardly room here to describe fully the virtues of the K2. A new Asahi conception, the Pentax K2 is the ultimate in SLR design for the advanced amateur and the professional.

Outstanding, is the newly developed Seiko/Asahi metal vertical-drop shutter. There is no jerk, inertia or speed-up, just perfectly even, electronically delivered exposures. The new shutter gives (a) continuous stepless speeds frm 8sec to 1/1000 sec in the manual mode, in both cases with full open-aperture metering. This gives total control. Electronic flash can be used up to 1/125sec, facilitating outdoor fill-in.

For against-the-light or spotlit subjects the exposure factor control has been extended to two full stops above and below 1X, with full interpolation. The mete is the latest rapid-response Silicon Photo Diode type, activated by a pair of silver oxide 1.5v batteries. metering is 70% centre-weighted, and based on the same efficient current saving/readiness principle as in the Pentax KX. Pull out the wind-on lever 2-% and the current flows to the meter. Take the first pressure on the release button ad the meter reads. Push in the wind-on lever or lock the release button and the current flow is cut off.

Meter sensitivity is EV1-18 with 100 ASA and ASA speeds 8-6400 can be set on a collar around the camera throat.

The K2 viewfinder gives the best combination of simplicity (for composition) and read-out (for creative control). The circle of microprisms is angle to give snap-in, snap-out focusing with the focal length range 28-135mm. For more extreme focal lengths the plain groundglass collar can be used. The speed in use is read at the right of the viewfinder screen. On auto, the needle floats to the speed, on manual you simply turn the aperture ring until the needle matches a green bar indicating the set speed.

Above all, the K2 has a larger mirror giving an extremely bright image and avoiding screen cut-off with lenses of 400mm or longer.

What used to be the depth-of-field preview switch on previous models (not required on KM or KX models) becomes the mirror lock-up on the K2. When set at auto, the shutter speed knob locks, while a small chrome button frees it for manually selected speeds. Depth-of-field preview is by the button above the 5-9sec self-timer lever.

Other features:

  • Most of the electronics in the K2 are at the right, so the pentaprism housing and throat are shifted slightly left. This has the incidental advantage that the wind-on lever can be stroked without shifting the lens off axis while viewing.
  • Coaxial flash sockets are now at the left of the top-plate.
  • The large, fast rewind knob crank is angled to keep the fingers well away from the pentaprism housing.
  • A roller beside the pressure plate ensures dead flatness of the film.
  • There is a reminder pocket on the back to take the film carton tab.
  • The left front edge of the baseplate is chamfered for smoother grip.

The new cameras have new-fitting lenses with special Pentax bayonet mount. There is a new, larger throat which will permit the development of ultra high speed lenses in various focal lengths. The standard range already includes a 50mm f/1.2. The SMC Pentax lenses are inserted simply by matching two dots (a raised bump allows this to be done even in the dark) and giving a quarter turn clockwise. Lens changing is thus a speedy operation. The SMC lenses have a larger focusing grip and filter size for the standard and most medium focal length lenses is now 52mm. These lenses are SMC coated on all surfaces, not just air/glass surfaces, but optical formulae are the same as for SMC Takumars. There is a full range of open-aperture metering SMC Pentax lenses from 17mm f/4 fish-eye to 300mm f/4, plus 50mm and 100mm f/4 macro, 45-125,, f/4 and 85-210mm f/4.5 zoom. Stop-down metering SMC Pentax lenses include 400m f/5.6, 500mm f/4.5, 1000mm f/8 and 135-600mm f/6.7.

A simple K adapter ring permits Super-Takumar and SMC Takumar lenses to be used on K Series Pentax cameras. Metering is by stopping down the aperture ring, as the auto-diaphragm will not function. A full system of K accessories will be available.


Hope you found this article interesting, please leave any comments below. If there is anything from the Pentax history that you would like us to find in the Pentax User archives please let us know!

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