These elements can be made by 1) expensive manual grinding, 2) molded plastic, 3) Leica's patented "press" process, where the element is pressed into an aspherical ("non-spherical") shape. ASPH lenses, however, involve usually 1 element that does *not* have a constant radius of curvature. This design however restricts the number of optical corrections that can be made to the design to render the most realistic image possible. These are easy to manufacture by grinding while "spinning" the glass. Most lenses have a spherical design - that is, the radius of curvature is constant. ORIGIN mid 19th cent.: from a- + Greek stigma 'point' + -ism. ORIGIN late 19th cent.: from an- 1 + astigmatic (see astigmatism) :Īstigmatism a defect in the eye or in a lens caused by a deviation from spherical curvature, which results in distorted images, as light rays are prevented from meeting at a common focus. Produced again as a retro camera in 2000-2002).Īnastigmatic (of a lens system) constructed so that the astigmatism of each element is canceled out. If you are looking for the Leica Compendium (2012 print edition and 2014 digital edition) by Erwin Puts, please wisit his website for more info, or try search eBay for his books (usually sold out from the publisher rather fast, so they become collectors items).Ĭourtesy o f Oxford American and See my more complete list of definitions at my article Leica DefinitionsĪnastigmat an anastigmatic lens system ( Leitz Anastigmat (Leitz I) from 1920 with a fixed 50mm f3.5 lens. From Ur-Leica to Leica R8 and M7 illustrated.
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