Pentax Auto 110 - Auto 110

Auto 110

The Pentax Auto 110 featured fully automatic exposure, with no user-settable exposure compensation or adjustments. Metering was TTL (through-the-lens) and center-weighted. Unlike 35 mm SLRs, the system's lenses did not have a built-in iris to control the aperture. Instead, an iris was mounted inside the camera body, and functioned as both an aperture control and a shutter. This mechanism was capable of programmed exposures between 1/750 second at f/13.5; and 1 second at F/2.8. To ensure that light travelling past the diaphragm blades could not get through to the film over time, the camera's mirror system also functioned as a light-tight seal when in the viewing and focusing position. Since the iris was part of the camera, all of the system's lenses had to be constructed with an f/2.8 aperture. The lens' designs, based upon the film dimensions, resulted in the 24mm lens being the 'normal' focal length, while lenses of wider angles or longer focal lengths were larger.

The camera detected the film speed by the presence or absence of a ridge on the cartridge, as specified in the Kodak 110 film standard. Since there was no official specification of what the film speeds should actually be—they were just "low" and "high"—film and camera manufacturers had to decide for themselves the meaning. Pentax chose 100 and 400 ISO as their settings. A film with a 200 ISO speed would result in either under-or-over-exposure. The exposure latitude of the then existing color print films was about 2 f/stops (meaning that a photographer could expose either 2 f/stops under or 2 f/stops over the exposure set by the camera). Unfortunately, more recently produced 110 film is rated at 400 ISO, but is packaged with the ridge indicating 100 ISO. This ridge must be removed for the camera to expose correctly. Since only a few 110 cameras ever supported the ISO auto-selection, this does not affect the majority of cameras using the format but does affect the Pentax Auto 110.

The camera was offered in a special edition "Safari" model, identical to the Auto 110 except for the brown-and-tan color scheme.