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French Varilux Logo. Varilux is a brand name belonging to Essilor International, a producer of corrective lenses.The first version of the lens was invented by Bernard Maitenaz and released in 1959, and was the first modern [clarification needed] progressive lens to correct presbyopia.
The Carl Zeiss AG & Varilux lenses were the first PAL of modern design. Bernard Maitenaz, patented Varilux in 1953, and the product was introduced in 1959 by Société des Lunetiers (now Essilor). The first Varilux lenses' surface structure was however still close to a bifocal lens, with an upper, aberration-free half of the surface for far ...
There is no precise definition of the term, but lenses marketed as "standard zoom" usually cover a range of at least 30mm to 70mm in terms of 35mm equivalent focal length with an optical zoom ratio of 2.5× (e.g. 28-70mm) to 5× (e.g. 24-120mm) — the most common being 3× (e.g. 24-70mm). [1]
35 mm equivalent focal lengths are calculated by multiplying the actual focal length of the lens by the crop factor of the sensor. Typical crop factors are 1.26× – 1.29× for Canon (1.35× for Sigma "H") APS-H format, 1.5× for Nikon APS-C ("DX") format (also used by Sony, Pentax, Fuji, Samsung and others), 1.6× for Canon APS-C format, 2× for Micro Four Thirds format, 2.7× for 1-inch ...
After many years as rivals, Essel and Silor merged on 1 January 1972 to form Essilor, then the world's third-largest ophthalmic optical firm. [1] Its first year of existence was marked by the creation of Valoptec, a non-trading company composed of stockholder managers who held half the company's capital stock, and the purchase of Benoist-Bethiot, a French lens manufacturer specializing in ...
Corrective lenses provide vision correction over a range as high as +4.0 diopters. People with presbyopia require a convex lens for reading glasses; specialized preparations of convex lenses usually require the services of an optometrist. [15] Contact lenses can also be used to correct the focusing loss that comes along with presbyopia.
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