|Agfa Isomat-Rapid (1965 -1969)|
image by Hans Jan Dürr (Image rights)
The Isomat Rapid outwardly resembles Agfa's simple fixed-focus Rapid models like the Iso-Rapid I; and like those, it gives 16 square exposures of 24×24 mm per roll. Interlocks only allow the shutter to fire with the back closed and film advancing; and a frame counter behind the shutter release counts down the exposures remaining. (After the 16th exposure, the film advance will turn continuously but the shutter locks.)
But the Isomat Rapid is a more sophisticated model, with weightier body and a scale-focusing, three-element Color-Agnar 38mm f/4.5 lens. The feet/meter distance scale is inconveniently located underneath the lens; instead simple pictograms face upwards towards the user. For two of these, the focusing scale has click-stop detents. The black-faced version of the camera has a "two heads" icon that is strangely chosen: When focused at this distance, the lens's field of view is actually well over a meter/yard high. The white-face camera has a more suitable icon, showing the whole torsos of two people.
While one might suspect that the "fly eye" panel beside the viewfinder might be a dummy light meter (as on other cheap snapshot cameras), this is a true selenium cell, which automatically adjusts the diamond-shaped lens aperture opening as the photographer presses the shutter release. If this aperture is within the available range of f/4.5–16, an indicator dot at the right side of the (not terribly accurate) viewfinder switches from red to green, indicating proper exposure. The camera has a fixed shutter speed, nominally 1/70th second, in autoexposure mode.
For flash exposure using the included hot shoe, a tab on the side of the lens permits manual selection of apertures. When using these settings, the shutter speed switches to approximately 1/30th of a second, to accommodate the burning time of bulb flashes.
The Isomat Rapid takes advantage of one advanced feature of the Rapid film standard, namely its emulsion-speed index tab. Whenever a photographer purchased a fresh roll of Agfa Rapid film, it would come loaded into a cassette with a tab encoding the appropriate film speed. This allowed a suitably-equipped Rapid camera to adjust its meter readings accordingly. The indexing key is a silver metal plate affixed to the side of the cassette, whose central tab is shorter for slow films and longer for fast ones. (Empty cassettes of any speed could be used in the film take-up compartment. Rapid rolls had the emulsion type punched into the loose tail of the film to remind the photographer which kind had just been shot.)
Rapid loads were standard perforated 35mm film, so today's photographer does not find it too daunting to reload empty Rapid cassettes in a darkroom; but the speed-index system does create the extra headache of locating (or modifying) cassettes for the correct tab length.