Film Friday: A closer look at the Pentax KX, an original K-mount SLR: Digital Photography Review

Photo credit: Anno Huidekoper

The Pentax KX was the successor to the Pentax Spotmatic F, but it is far more than just a fancy F. Introduced in 1975, it was one of the first Pentax K-mount SLRs. With this new series of cameras, Pentax replaced the screwmount lens type with a bayonet mount system. The K-Series cameras were pretty large and heavy compared to the cameras that came before, but they went on to gain impressive features throughout the 1970s.

Alongside this classic K-mount body, Pentax also introduced 26 K-mount lenses. Some lenses – like the SMC Pentax 30mm F2.8, SMC Pentax 120mm F2.8 and SMC Pentax 150mm F2.8 – are well-regarded to this day. A 24mm F2.0, an 85mm F1.4 and some ultra telephotos for birding came along after the camera launch.

The Pentax KX and its contemporaries

Having been introduced in 1975, the Pentax KX was retired in 1977 when the more compact Pentax MX and ME cameras were released, perhaps in response to where the competition of the time was going.

Three years prior to the KX, the impressively small Olympus OM-1 was introduced. The OM-1 was an all-mechanical SLR. It had a large viewfinder with interchangeable focusing screens but a fixed prism. A motor drive could be attached. All Pentax K models were bigger and heavier.

Photo credit: Anno Huidekoper

In 1976 the Canon AE-1 was introduced, with more electronics, again smaller and lighter than the Pentax KX as well as cheaper. Maybe a bit more plasticky, maybe a bit stripped-down. But who cares? The AE-1 was an instant success!

Nikon’s FM, introduced in 1977, was also a bit smaller, had a faster and very affordable winder and had interchangeable focusing screens. And maybe more importantly, it had a much wider range of lenses.

Features

There’s a big upgrade under the hood compared to the Spotmatic F it superseded: the KX has a Pentax-made all-mechanical focal plane shutter of rubberized cloth. Since it’s mechanical and not electronic, all shutter speeds are still available whether or not the camera has batteries. However, the shutter provides electronic flash sync only up to 1/60 sec.

Photo credit: Anno Huidekoper

As the shutter mechanism of the KX is completely different than the Nikon FM’s, rubberized cloth versus metal, you would expect a difference in noise level. But these two competing models produce more or less the same amount of noise (although it’s worth noting that the mirror of the Nikon is a lot bigger).

The KX has an optical reflecting system that shows you the aperture setting of the lens. At the right you see in the finder a vertical shutter speed scale. The view through the finder gives a slightly smaller than life-size view.

A special, and very rare, version of the camera was the KX Motor Drive. This model had the capability to couple to a motor drive that included a pistol grip. It could do only 3 frames per second, it was heavy and pretty expensive.

Photo credit: Anno Huidekoper

One big difference between the low-cost Pentax KM and the KX was the light meter material: cadmium sulfide (CdS) versus silicon-diode. The latter works faster and is more reliable. The KX meter-coupling range was also far greater than that of the KM. Like all Pentaxes, the metering is center-weighted. The meter is on when you cock the advance lever and press the shutter release down halfway. The system can be turned off by pushing the lever back to the body. It is a convenient system but perhaps not the best setup for left-eyed users.

Photo credit: Anno Huidekoper

The KX is just a bit bigger than the Nikon FM. But, in typical Pentax form, its rounded design makes it feel smaller and the handling is superb overall. The three-claw stainless-steel bayonet makes changing lenses very easy and the lens release lock is well-designed.

Final thoughts

The Pentax KX was the top manual-exposure model of the K-Series. It had a lot to offer: a depth-of-field preview, a mirror lock-up and a self-timer. It remains a well-built camera with exceptional handling. The viewfinder gives you plenty of information at a glance. The silicon-diode metering works fast and changing lenses is very easy. A new owner of this old camera will appreciate classic Pentax primes like the 28mm F2.8, 50mm F1.8 and 135mm F2.8.

Although the mirror is small, the sync speed is slow, and no affordable motor winder add-on was manufactured, the Pentax KX still excels in many areas.

About the author

Anno Huidekoper is a (street) photographer and designer. He has developed his own metal passe partout line that makes it easy to frame photos. See his work and read more on his website.