Archived posting to the Leica Users Group, 2007/03/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Aha, at the time I read that Leica had gone from ground to hot pressing (in a Leica leaflet) the 90mm asph did not yet exist. Anyway, as you say, it is the cost which differs. This was the point I was trying to make - asph lenses are not necessarily dearer than spherical when the aspheres are pressed rather than ground and the aspherical surface simplifies the rest of the optics. Frank On 11 Mar, 2007, at 18:16, Sander van Hulsenbeek wrote: > Frank Dernie wrote: > > "AFAIK the Leica lenses which have ASPH rather than ASHPERICAL > engraved on them have hot pressed rather than ground aspherical > elements. This type of element is not too expensive and it can > simplify the rest of the lens design. I am guessing this is why the > new lens is less expensive than the one it replaces." > > That not quite what I understood in Solms a little more than a year > ago: > > Aspherical lenses from Leica come in 2 varieties: hot-pressed and > ground. The latter process is the more expensive, but the choice > between them is just because of the size: there is a limit to the > diameter for which aspherical lenses can be hot pressed. > > So it is quite possible that the asherical lenses in big tele's, > including the 90/2 ASPH, and perhaps the 75/2 are ground, while the > smaller lenselements in the wide angles are hot-pressed. > > However, the polishing and quality control process (with > complicated wave interfererence lens testing machines) for both > kinds is the same, and for the end result the way the glasselement > started its life is of no consequence. ASPH and ASHERICAL: it is > all the same. > > Yes, the hot-press to final lens process is cheaper, and that is > reflected in the price of your lens. The lensquality should be the > same for all. > > Sander > Amsterdam > Holland > > > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information