In the mid-1970s, Olympus rethought the SLR and introduced its OM-1, proving that a small-bodied camera could be dependable and commercially viable.
It took a couple of years for its Japanese competitors to jump on board and develop their own smaller cameras.
Among them was the Pentax "M" cameras - the MX and ME. Other models would follow.
The MX was the smallest of the downsized 35mm SLRs, as I recall. It is an all-manual camera with its two S76/LR44 batteries only needed to power the gallium arsenide phosphide light meter. Most camera makers were looking for alternatives to the cadmium sulfide (CdS) cells, and by and large they moved to silicon blue cells. I think the MX was the first (and possibly only) camera to use gallium arsenide.
If the batteries die, you can continue shooting, as its cloth focal-plane shutter requires no electrical current.
The MX is a system camera with interchangeable viewing screens, an autowinder, a motor drive, a 250-exposure back and a large number of "M" and "K" lenses that use the Pentax K mount.
The suitably large and bright viewfinder displays the shutter speed on a semicircle, so you can see the nearest two speeds, the aperture via a small window that looks down on the lens' aperture scale and five LEDs to guide you to the correct exposure.
I've always felt that the shutter speed dial on the top of the camera is too tightly sprung. That is, it takes too much effort to turn the dial, which makes it difficult to quickly change shutter speeds when you're looking through the viewfinder.
I've often said the camera is too small. Don't get me wrong. I love the camera, but I think Pentax took the downsizing trend too far.
This was the third camera that I bought after a Cosmorex SE and a Konica 35 Automatic. Purchased in 1978, I shot my first roll of Kodachrome (25) with this camera. I also shot lots of black and white. I should note that my camera had a standard f/2.0 50mm lens, not the pancake lens seen in the photo above.
I later sold the camera to my brother and bought into the Nikon system. In the early 2000s, I bought an MX and once again enjoyed the fun of this diminutive SLR.