The camera allowed one to focus the lens at maximum aperture with a bright viewfinder image. After focusing, a switch on the side of the lens mount stopped the lens down and switched on the metering which the camera displayed with a needle located on the side of the viewfinder. The use of stop-down light metering was at the time revolutionary, but it limited the capability of the lightmeter, especially in low light situations. Later models Spotmatic F, Electro Spotmatic, ES, and ESII were capable of open-aperture metering when used with Super Multi Coated (S-M-C) Takumar lenses with an aperture coupling prong in the lens mount.
Honeywell was the U.S. importer of the Spotmatic. Cameras officially imported by Honeywell were labeled Honeywell Pentax, instead of Asahi Pentax. The Spotmatic IIa was only available as a Honeywell Pentax; it was sold exclusively in the USA and had an electronic interface for specific Honeywell Strobonar electronic flash units.