Toronto. Did you know Leitz made telemeters, or rangefinders before making their famous Leicas? The Leitz telemeters had a 1 metre or half metre spacing and were used to measure distances. In the days of view cameras, rangefinders were unnecessary since the image projected by the lens on the ground glass could be used to focus the camera.
When non-ground glass cameras became common, they simply used a small aperture and “fixed focus” or you could simply estimate or measure the subject distance and adjust the camera distance setting. The first known coupled rangefinder on a camera was sold in 1916/7 by Kodak of all people.
In 1924, the year before Leitz came out with the Leica, they made a smaller rangefinder that could be attached to a camera using its accessory (flash) shoe. The rangefinder was slid into the shoe vertically and a dial was rotated to make the two images of the subject merge. The reading (in metres or feet) was transferred by hand to the camera or lens setting for distance.
Various rangefinders were made by Leitz from about 1924 to 1966 for use on cameras without a built-in rangefinder. The rangefinders used various bases from the early 10.5 cm (8.3?) to the shorter 7.5 cm base and the even shorter post war chrome only model with a 6.2 cm (5.4?) base. Different diameter wheels were used to improve accuracy and they came in black enamel or chrome to match the camera. Measurement was either in metres or feet to match the lens. Some special versions were made for use on cine cameras or the Nagel Pupille still camera.
Of course modern digital cameras use the image on the sensor much like old view cameras and mid last century SLRs to set the lens to subject distance. The sharpest subject focus determines the setting used. I bought my FOKOS in January 1985 from Bill Belier. It was initially used on a Leica If. Earlier, at our June 1980 fair, I bought a black enamel FODIS
(FODUA) from Czaba Martoni of Michigan. It began life as an accessory for the original Leica camera.