The brand TOPCOR was always synonymous with the finest in optical quality. The top quality TOPCOR lens group include lenses from super-wide angle 20mm to telephoto 500mm, including a zoom lens, plus special macro lenses. Most of the lenses were designed for using a 49mm filter screw mount, for keeping equipment investment at a minimum, whenever possible.
Lenses with the "M" suffix are multi-layer anti-reflection coated for improved light transmission, elimination of flare and ghost images and superior color balance, as well as reducing light reflection at the lens surface.
Lenses with the "GN" prefix, such as RE GN Topcor 50mm f/1.4 and 50mm f/1.8, have a Flash-Matic system for automatically setting the correct f/number to the lens for the focused distance when the guide number (GN) of the flash bulb or electronic flash unit is first set to the lens and locked in. The Flash-Matic system eliminates the need for calculating the correct f/number in flash photography, as well as giving accurately exposed flash-illuminated photographs all the time.
All lenses with "Auto" included in their lens designations, such as the RE Auto Topcor, RE Zoom Auto Topcor, RE Zoom Auto Topcor and RE Macro Auto Topcor,as well as the two RE GN Topcor optics, have fully automatic instant opening lens diaphragm action and are automatically and mechanically coupled to the Mirror-Meter.
Lenses designated R Topcor have preset lens diaphragm action and are optically coupled to the Mirror-Meter, with exposure set by simply adjusting the aperture ring.