Archived posting to the Leica Users Group, 1998/06/07[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
<Do you know, off hand, what the wavelengths for C, D, and F are? C=6563 D=5890 F=4861 in Angstrom units= 10 power -7 mm <Are you saying Leica doesn't demand apochromatic correction across the <image field, edge to edge? I seem to recall Leica stating that very thing. If a lens system is APO corrected it is apo corrected all over the field. But some other aberations can diminish the image quality in the outer zones. If Eric implies that a lens can be fully apochromatically corrected in the centre and be non- or partially-apochromatically corrected in the outer zones, I at least must pass. <I seem to recall Leica stating that very thing. I have no knowledge of this particular claim by Leica. <And your comment about glasses having apochromatic characteristics is <misleading, no? No particular glass could be so described. It's a <combination of glass elements that brings about apochromatic correction. Do <you mean some glasses have high refractive index and anomalous dispersion <characteristics which makes such correction possible? Yes my statement is misleading. Thanks for pointing your finger at it. To create apochromatic correction you need three glass types some of them of anomalous dispersion character. There is no APO glass. ( I said that myself in an earlier post, but I was to hasty in my wording). What I meant to say is that some glasses have characteristics that can advantegeously be used in combination with others to create APO correction.