Archived posting to the Leica Users Group, 1998/06/06
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Thanks, Erwin, for this particularly lucid description. At 06:20 AM 6/6/98 , Erwin Puts wrote: >fringing. Normallnses are corrected for two wavelenghts (Fraunhofer lines). >mostly F (hydrogen: blue) and C (hydrogen: red). For achromatic correction >the F and C imges are equal and so all wavelenghts between these two are >also corrected. But there are many wavelenghts still uncorrected. That is >called the secondary spectrum or 'amount of residual colour'. A lens that >is apochromatically corrected, has three Fraunhofer lines (C, D and F) >where aberrations are zero. But there is still some residual colour left. Do you know, off hand, what the wavelengths for C, D, and F are? - -Paul