ABSTRACT
The high resolving power and superlative image quality of well-corrected lenses is not always desirable or necessary. While for scientific or technical photography the RP and contrast of a lens are important, for subjects such as portraiture, ‘atmospheric’ landscape pictures, and surreal images for advertising purposes, a certain softness of definition is desirable. Where it is convenient to purchase a special-purpose soft focus lens for occasional use, various methods are used to obtain reduced definition from a lens by both mechanical and optical means. Another popular method of inducing spherical aberration to give soft focus is by deliberately altering the separation of a pair of elements in the lens configuration. Autofocus cameras may have a soft focus mode available with conventional lenses, in that a zoom lens may be altered in focal length during a short time exposure, or a fixed lens adjusted slightly in focus similarly.
