The Robb Collections: I took apart the World's Smallest SLR Camera: Pentax Auto 110

March 6, 2018

#236

Gentle reader,

Kodak may have invented drop-in film called "Instamatic" during the 1960's for their first iteration of easy-loading-no-rewinding films that utilized 35mm film (missing the usual sprocket holes) and in black plastic cartridges (or cassettes if you prefer). The film was paper-backed with frame numbers showing through a rectangular hole in the back of the cartridge. The film's number was 126. IT produced square images. A few years later, they came out with "Pocket Instamatic" that used 16mm in the same manor, but was called #110 film.

Other camera makers took up the banner (or jumped upon the bandwagon) by making cameras of their own that used 126 and 110 film. Other film companies made 126 and 110 film, no doubt having to pay Kodak royalties, too. As far as the latter film, Japanese makers, Minolta and Pentax made SLR cameras to use the tiny film cartridges.

Pentax Auto 110 is on the left with it's 24mm "normal" lens similar to 35mm cameras 50mm lens. Minolta is on the right. Much bigger camera with a large zoom lens. But still tiny compared to 35mm film and digital SLR cameras.

Below is another, non-working, Pentax Auto 110 camera that I decided to disassemble to find out why it stopped working and, frankly, to see how they crammed a working Single Lens Reflex camera with interchangeable lenses into such a tiny body.

The battery box is one the left of the main body, it's contents: two A76 batteries had been left in the camera and started leaking corrosion. They fit in the device below the battery box (looks like a B) which cleverly held the two batteries facing opposite directions and made for easy removal and installation. The cancer of corrosion spread throughout the camera's components. It can be clearly seen on the flat metal piece to the right of the black lens housing frame. The components that attached to that would not move as a result. Untold numbers (millions?) of cameras died a similar fate through ignorance. Easy to do, how many flashlights have you had that were thrown out because the batteries started leaking? Flashlights are cheap, cameras are not. Technology has helped by making rechargeable batteries and devices that let us know it's time to recharge them.

The part with all the wires attached (above) to it is the electronic brain of the camera. I have removed those circuit boards and placed them in the box I take to the local Haz-Mat facility for proper disposal. I decided to photograph the "heart" of the camera and show those images below:

Starting with the viewfinder opening. We are looking into it and see the image on the mirror. That image is blurry because there is no lens attached to it.

From the photographer's perspective (behind the camera) this is the mechanisms on the left side of the heart. The viewfinder and prism are on the left in the image above.

The other side with the viewfinder and prism on the right. Two levers only for actuating the mirror/shutter mechanisms.

This is the bottom components. This (and all SLR cameras) is extremely complex and I salute the Pentax engineers that created this tiny jewel. These components connected to the other levers and gears seen below the camera's bottom plate in the photo (above) of all the parts. They wound the film and reset the shutter.

Above is the top of the prism. See how they made a way to attach it without scratching the delicate mirror coating that reflects the light inside the prism? The viewfinder is at the top.

Above is the opening that the light travels through from the lens to the mirror and film. The darker piece worked the two leaves of the aperture. The aperture controls the size of the opening needed to correctly expose the film. You can see the mirror and what is behind the viewfinder in the hole.

The front of the prism. These SLR prisms reverse the image and turn it right-side-up for the photographer. All with no moving parts. Below is another view of the top with the viewfinder at the right edge of the photo.

While it looks like the inside of a chimney as seen looking up from the fireplace, it is the back of the mirror with a second door/shutter that drops down the same time the mirror is flipping up to make the image on the film. Opens and closes like a clam's shell. This design kept the body thickness shallower.