The Pentax Kx is part of the legendary K series of SLR cameras introduced in 1975 introducing K mount bayonet lenses, replacing the Spotmatic series M42 screw mount system.
Pentax respected photographer’s investment in quality lenses by making an adaptor so photographers could use their existing lenses on the new K series cameras.
The Kx is from the model range that produced the legendary Pentax K1000 SLR that introduced many photographers to SLR photography. Pentax kept producing the K1000 from its introduction in 1976 right through to 1997. The Kx was a mid range model while the K1000 was the base model.
The Kx is a completely manual SLR camera where the photographer sets the aperture and shutter speed, using the light meter display in the viewfinder as a guide.
The light meter in the Kx uses silicon photo diodes instead of the older Cadmium Sulphide diodes in the K1000. The Kx also had a greater film speed range of 8-6400, compared to the K1000‘s 32-3200.
The Kx has a quirky innovation, a second lens for the viewfinder in the pentaprism housing giving a view through the viewfinder of the selected aperture. Of course using a Pentax lens helped to ensure the aperture ring lined up correctly with the viewfinder.
Light Meter
The light meter in the Kx uses a Match Needle system in the right of the viewfinder. The light meter measures the light coming in Through The Lens (TTL metering) and a black needle goes higher indicating a bright scene, and lower for lower light. The blue needle is controlled by the shutter speed dial and points to the selected shutter speed on a scale in the viewfinder.
The black needle responds to changes in aperture, while the lens stays fully open until the shutter operates. This modern feature, called open aperture metering, had only just become common. Before this SLRs used stop down metering system where the lens aperture is closed down to the selected aperture for metering, making composing and manual focusing difficult at small aperture settings, so photography was a two part process.
The Kx has a Centre Weighted light meter, giving more importance to the centre part of the image frame. The photographer evaluates the scene and guided by the light meter set the final exposure settings.
Focusing
Autofocus SLRs did not exist in 1975 so photographers had to judge if the image in the viewfinder is properly focussed.
According to the owner's manual this Kx came with a cross-microprism focusing system. In a in the centre of the viewfinder the microprism broke the image up into dots, unless it was properly focussed.
It is up to the photographer’s skill and experience to focus the lens properly on the subject. One of the pro tricks is to look for objects at same distance away as the subject with sharp contrast-y edges and use these as the focus point.
Frame Rate
Some sports photographers use the machine gun approach to photography. The frame rate of the K series depended on how fast the photographer could press the shutter button and wind on the next frame of film. In the real world this often meant only one shot of incidents, so photographer’s had to choose the best moment to take the photograph.
The Camera Body
This feels strange after years using Digital SLRs. The Kx has a very flat body, especially on the right hand side around the shutter button. Modern DSLRs have shaped grip sections protruding forwards.
Image Quality
The Kx came with one of Pentax’s prime lenses, in this case a 55mm f1.8, in an era when the kit lenses were usually amongst the camera manufacturer’s best.
A large contributor to image quality came from the choice of film. The Kx could take any 35mm film mounted in standard cartridge. The choice for film photographer ranged from cheap print film right up to expensive professional transparency film.
Shoot With Flat Batteries
The Pentax Kx does not rely on batteries, it is purely mechanical. Winding the film onto the next frame also tensions a spring in the shutter mechanism that powers the next shutter operation. The batteries only power the light meter that is only a guide to exposure.
One exposure guide is called the “Sunny f/16 rule” where for a ISO 100 film on a sunny day set the aperture to f16 and the shutter speed to 1/125 second. Using this as a starting point photographers can estimate exposure for darker conditions or when different shutter speeds are desired.
Shutter
The Pentax Kx’s shutter is the old horizontal run mechanical unit using a rubberized silk curtain. This is a basic design and on this particular Kx it lasted until the late 90’s. The Kx was swiftly repaired and continued in regular use until it was overtaken by digital technology.
The top of the line K2 had a more modern shutter assembly, an electronic vertical run metal bladed shutter similar to those found in current Digital SLRs.
The Digital Demise
This Kx travelled the world in jet planes or toured parts of Australia on a motorcycle for thirty years, but the needs of photojournalism and deadlines finally caught up with Kx. The ability to shoot and immediately edit and publish digital images is too great an advantage so the Kx retired to the cupboard.
However, the lenses live on, the picture of the Derwent Entertainment Centre by the river was taken using the original 55mm kit lens. Only now it is on Pentax’s latest Digital SLR, the K-5.
For more technical information visit Bojidar Dimitrov's Pentax K-Mount Page
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