Rotating The Lens Until: However, although a long focal length lens is mandatory, it need not be expensive. The utmost of critical sharpness in a portrait lens is not necessary, or even desired, since considerable diffusion can be tolerated in portrait negatives. Your lens needn't be in a shutter for strictly studio portraits, either. A lens in barrel is perfectly satisfactory, since you can provide yourself with a simple Packard shutter to use behind the lens. Many portrait men actually prefer the Packard to the more costly between-the-lens shutters.
In 1932 Zeiss Ikon brought out a similar camera, the Contax; it featured a built-in rangefinder coupled with the focusing mechanism so that by simply rotating the lens until a double image of the subject became single, the photographer was assured that the image would be in focus. Soon lenses with apertures as large as //1.5 were offered for the Leica, the Contax, and a host of other 35mm rangefinder cameras. A further refinement was the provision of single-lens reflex viewing on a ground glass observed at eye level through a prism, as in the highly popular Nikon F, introduced shortly after World War II by Zeiss Ikon of Dresden as the Contax S.
The first lens designed specifically for photographic purposes was Petzval's 1840 portrait lens. The images formed by this lens showed great loss of definition at the corners of the plate-a fault more theoretical than practical in portraiture, where edges mattered little. For outside work, however, particularly in photographing architecture, a lens with a flat field was desirable; and one free of spherical aberration, which caused straight lines to be imaged as slightly curved, was essential.
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Photography
