the late 1980s.Jason Schneider, "50mm: How do seven leading normal lenses compare? We put 'em to the test!" pp. 42–49. Popular Photography, Volume 98 Number 5; May 1991. . p. 42 Ponder & Best's designed in the USA/made in Japan Vivitar Series 1 lenses were among the best available (many were the first of their kind) for about a dozen years, before new owners debased the brand. 1975 E. Leitz APO-Telyt-R 180mm f/3.4 (West Germany): first apochromatic lens for consumer cameras (Leicaflex series SLRs). The refractive index of glass increases from red to blue of the light spectrum (color dispersion). Blue is focused closer to the lens than red causing rainbow-like color fringing (chromatic aberration).Kingslake, pp. 71–72, 316, 317Peres, pp. 175, 712, 717Stroebel and Zakia, pp. 424–425 Most photographic camera lenses are achromatically corrected to bring blue and red to a common focus – leaving large residual green and violet chromatic aberrationsRay, pp. 54–55 that degrades image sharpness; especially severe in long focus or telephoto lenses. If red, green and blue are brought to a common focus (plus other aberration corrections) with very little residual aberration, the lens is called apochromatic.Kingslake, p. 316 Chromatic aberration was an issue at the dawn of photography (daguerreotypes [invented 1839] were blue sensitive only, while the human eye focused primarily using yellow), but apochromatic photographic lenses were considered unnecessary until the dominance of color film. The use of extra-low dispersion glasses made most 1980s professional telephotosBennett Sherman, "Techniques Tomorrow: New glasses make the optical scene brighter and clearer. What are they and what are they doing?" pp. 10, 14. Modern Photography, Volume 48, Number 8; August 1984. and many 1990s amateur telephoto zooms apochromatic. 1975 Mamiya M645 (Japan): first 645 medium format system SLR. Took fifteen exposures of 2¼×1⅝ inch (6×4.5 cm) nominal frames (56×41.5 mm actual frames) on 120 film."Modern Tests: Mamiya M645 Super: Advanced Full-system 6×4.5 cm SLR?" pp. 46–55. Modern Photography, Volume 50, Number 9; September 1986. Mamiya was never successful at producing 35 mm SLRs, despite a half dozen attempts between 1959 and 1980. However, it was a leader in medium format cameras; first with the Mamiya C series (1956, Japan), the only successful interchangeable lens twin-lens reflex (TLR) cameras ever made,"Modern Photography's Annual Guide to 47 Top Cameras: Mamiya C330" p. 135. Modern Photography, Volume 36, Number 12; December 1972. and then with the RB67 (see above) and M645