Archived posting to the Leica Users Group, 2000/02/13
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Mark Rabiner wrote: > "A.H.SCHMIDT" wrote: > > > > At the time, when the Pentax Spotmatic was released, Pentax advertised a Ghostless > > UV filter. > > > > This filter did not have a flat ground glass, but it was curved. A similar curve > > like the front element of a lens. Pentax in their leaflet says: "The Ashai > > Pentax Ghostless Filter is a breakthrough in filter design. With this curved UV > > filter, the image light reflected back to the Ghostless filter and retransmitted > > through the lens, forms a duplicate image in the air, thus eliminating a ghost > > image on the film plane." > ><Snip> > Would not introducing a curve into a filter make it act like a lens? I'm > surprised it did not change the "power" of the lens!! > Mark Rabiner Mark, you have a point there. Maybe it does not work like an extra lens, because it has a uniform thickness and has the same curvature as the front element. Jim Brick also replayed with an answer that makes sense. All I can say, I never noticed any difference with this filter on or of on the Pentax lens. Maybe it is just a coincidence. Maybe some optical expert can put some more light on to it (hope this does not introduce ghosting) Regards, Horst Schmidt