'Argh!!!' is likely to be the response from a youngish photographer when first asked to look through the rangefinder and viewfinder of a 1930-40s camera. These finders are small and dark--often described as 'squinty'. During these two decades, camera and optical designers moved from finders that were the initial developments beyond groundglass focusing to finders that were reasonably bright and could be used to capture scenes that required selecting from several visual elements and even scenes with movement.
Through the 1920s, most Kodak cameras were of the box or folder design and had some form of brilliant waistlevel finder or a simple non-optical frame set for eyelevel use. These forms of viewfinder continued to appear on inexpensive Kodaks throughout the 1950s. In the mid-30s, during Kodak's exploration of the highend market, optical eyelevel finders began to appear in the Bantams, 35mm models and the larger roll film cameras, sometimes with rangefinder companions.
Prior to 1930 few cameras had rangefinders. Early cameras had relatively slow lenses that were used outdoors. Because of the slow emulsions, indoor shots tended to be posed, giving the photographer time to accurately measure distances. Early miniature cameras had fixed lenses with focal lengths that had considerable depth of field. All of these issues mitigated against the need to include rangefinders. As films and lenses became faster and interchangeable long-focus lenses were introduced to miniatures, the need for accurate focusing grew. Photographers extended their shooting styles to include candid and moving subjects where focusing needed to be more responsive.
The first handheld camera with a rangefinder was the Kodak No. 3a Autographic of 1916; these were built in various models into the 1930s. The original Leica of 1925 had only a viewfinder, but the 1932 Leica II had a separate rangefinder and, in 1932, Zeiss introduced the Contax, with rangefinder, to compete with the Leica. Rangefinders on larger format rollfilm cameras began appearing more regularly at about the same time. The Voigtländer Prominent had an uncoupled, split-image rangefinder in 1932, while the Bessa got its first uncoupled rangefinder in 1936. Zeiss introduced rangefinders on the Super Ikontas in 1935. The first 'modern' Kodaks with rangefinders were introduced in 1936--the Nagel Retina II, a followon to the successful Retina of 1934, and the domestic Bantam Special, a premium model of the Bantam that had been introduced with a new 828 film size in 1935. Joseph Mihalyi, a designer at Kodak, became a specialist in rangefinders, and the advanced designs in the domestic Kodaks were his. Even after rangefinders were introduced by Kodak's competition, Kodak used them sparingly in camera designs. In addition to Kodak's early exploration of the rangefinder feature on the Autographics, of the Kodak folders, including the Bantams, only the domestic Bantam Special, Super Kodak 620, the German Retinas and Regents, and one late model 6x4.5 Duo had rangefinders. The Ektra had its own rangefinder design required by its interchangeable lenses. In later model designs using tube lens mounting, only the Kodak 35 Rangefinder, Medalist, some Signets, Bantam RF, Chevron, 800-series Instamatics, and some late Retinas had rangefinders.
Design. From the beginning of their appearance in cameras, rangefinders
varied in design. While they all depended on bringing two images into
coincidence, they used different optical designs and the images created
differed. Split-field rangefinders create a view in which the top half
is from one window and the bottom half from the other. The superimposed
viewfinder produces a window within a window with the smaller rectangle
or triangle being produced from one rangefinder window within a larger
image from the other window. Focusing brings these images into coincidence.
While the drawing above would suggest that split-field and superimposed rangefinders would do the job equally well, the difference in engineering strategies necessary to implement the designs meant that they did not perform equally well. Magnification could be added to the split-field type rangefinder to make the image more visible and to sharpen the point of division between image halves. The exact position of the eye relative to the finder was critical, however, and the magnification used made them difficult to combine with viewfinders, which were usually minified. This design works well when focusing on images with distinct vertical elements; in a scene with mostly horizontal elements, the camera must be turned diagonally or vertically, disrupting whatever the user might have done to compose the picture in the viewfinder. Superimposed rangefinders seemed more intuitive to users and could be more easily integrated into viewfinder systems. Since either the larger or smaller window was colored to increase the contrast between the two, superimposed rangefinders were usually darker than their split-image counterparts. Because combined rangefinders and viewfinders required the same magnification, the rangefinder portion suffered from minification. The complexity of combining the range and viewfinders is shown in this drawing of the design of the Kodak Super 620 . In the Medalist and Ektra, Kodak tried to provide the convenience of the combined rangefinder/viewfinder with the accuracy of separate systems by placing the separate viewing windows very proximate to each other. The Medalist's minified viewfinder window is just above the magnified rangefinder window and located so close that it is only necessary to move the eye, not the head, downward about 15° to use the rangefinder. This design addresses the ergonomics issue created by the Regency design in which the rangefinder window is separated from the viewfinder window by 2 1/2 inches.
Manufacturing costs and increased complexity were also reasons that rangefinders were added cautiously. Virtually all Kodak folders used front cell focusing, where the front lens cell is mounted on a threaded cylinder that screws into the shutter . Focusing is done by referring to a focusing scale engraved on the rotating front cell, requiring only a single moving part. In contrast, coupled rangefinders required that the lens focusing action be linked mechanically or by a combination of optical and mechanical strategies to the rangefinder. Coupling mechanisms varied with lens mounting strategy. Since most small cameras had fixed lenses and bellows, the following comments relate to that design. In such cameras, a coupled rangefinder usually had one of two designs. In the first, the front standard was mounted on a movable rack that was mechanically linked to the moving mirrors, prisms or objectives in the rangefinder assembly. As the rangefinder mechanism was adjusted, the rack moved forward or backward on the drop down baseboard, as shown in this drawing of a Kodak Regent. A second rangefinder implementation method took an optical rather than a mechanical approach. The mirrors and prisms in the rangefinder were fixed. An additional optical element was added on the front lens standard which was in a fixed position rather than on a movable rack. As the lens was focused on the front standard, the secondary optic would move in a way that projected a movable beam of light to one of the range finder mirrors. The Bantam Special used this kind of design, with the lens in a helical mount , where the entire lens, not just the front cell could be moved forward and backward by means of the helical mechanism. As the lens was focused, the secondary optic was moved in an arc on the plane of the primary lens. This illustration of the Bantam Special rangefinder also shows how magnifying objectives and prisms are used in more complex designs to improve the accuracy of the rangefinder.