What is the Visitronic system?

The camera is equipped with five openings on the front: the lens, the cell window, the viewfinder, and two windows for the Visitronic system (also known as VA/F for Visitronic Auto/Focusing). These two windows are located on each side of the "Konica Auto Focus" inscription.

The system operates by triangulation, like a rangefinder, rather than by contrast analysis.

First, let's look at the VA/F assembly diagram in the C 35 AF (these photocopied diagrams come directly from Japan and the USA, annotated with felt-tip pen, re-photographed, filtered, retraced, and then photographed again as best as possible). From the subject (1), a mirror fixed at 45° (2) reflects an image into the VA/F (3). The rotating mirror (4), upon triggering, starts from the appropriate position it occupies for a subject located at 1.1 meters (approximately 43°) and rotates with perfect regularity to the position it occupies for a subject located at infinity (45°). During the rotation, the VA/F, which compares the two images reflected by the two mirrors, indicates (we'll see how and to what) the moment it detects that the two images on its two sensitive cells become identical. At this instant, the two beams converge on the subject. This is the principle of the rangefinder!... but classically, it is the eye that determines the moment of the superposition of the two images... whereas here, it is the VA/F that compares their identity.

At the moment the mirror (4) starts to rotate, the lens (5) begins to move back from the focus at 1.1 meters to the focus at infinity, under the action of the spring (6). Mirror and lens travel their course in exactly the same time.

 Returning to the VA/F, during the course, it indicates the moment of the identity of the two images to a "brain" (7). This instantly powers the electromagnet (8) which, by engaging the tilting pawl (9) in the rack (10) of the lens, stops its movement. The subject (1) is then in focus on the film (11).

Meanwhile, the automatic exposure meter measures the exposure, or in flash mode, the lens position controls the diaphragm, and the shutter release occurs. Because automatic EE exposure settings and VA/F focusing are ensured during the course of the shutter release! ± 1/30th of a second... A needle visible in a window to the right of the lens allows you to read, if desired, the setting used by the automatic focusing system (post-control).

During the next winding, the mirror and lens reposition themselves to 1.1 meters, waiting for the next analysis...

The VA/F is a set of integrated circuits and optics sold sealed to manufacturers who must associate the external components.

(Sources: Phot'Argus No. 83, November 1977)