Konica AR SLRs have a fairy unique light-metering system. Though quite simple, this system is very accurate. It makes use of the fact that, like in all cameras, light rays hit the focusing screen at an angle that is determined by the focal length of the lens used. With a telephoto lens, the vast majority of light rays hit the focusing screen perpendicularly, or nearly so. With standard lenses, some light rays hit the focusing screen perpendicularly, and some at an angle. The wider the angle of the lens, the greater the proportion of light rays hitting the focusing screen at an angle and the smaller the proportion of light rays hitting the focusing screen perpendicularly. With a 21m lens, perpendicular light rays are to be found near the center of the image only.
What makes Konica’s light metering system unique is that it uses two CdS photo-electric cells located on either side of the viewfinder to obtain a weighed average between two readings: The first cell measures general light levels over the entire frame. The second cell is aimed slightly below the center of the frame and is shielded in such a way as to favor light rays hitting the focusing screen perpendicularly. The combined readings of the two cells produce a weighed average that takes a greater or lesser area of the frame into account depending on the focal length of the lens mounted on the camera.
The foolproof aspect of this system has to do with the fact that it functions through purely optical means, as a function of the angle of the light rays penetrating into the body: The narrower the angle of the light rays entering the body, the wider the metering area on the frame and the greater the significance of the image's peripheral areas in the final weighed measurement. And inversely, the wider the angle of the light rays entering the body, the narrower the metering area and the lesser the importance of the sky in the overall average.
The system was improved over the years and the exact shape of the metered portion of the image varied slightly from one body to another, especially after Konica discontinued its large mechanical SLRs. In the days of the early Autoreflexes, this system proved to be one of the best metering systems in the industry. Good enough in fact for many professional Nikon users to mount their Nikkor manually-operated shift & tilt lenses on Konica bodies (using the Nikon lens to Konica body adapter) in order to take advantage of Konica’s metering system, which they found more accurate.
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