Archived posting to the Leica Users Group, 1997/11/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I have really enjoyed all the battering on this and that in this journal. By far I really believe the APO lens and by definition they should be. Chromatic lens were color corrected. What they did not tell us was they were corrected as best they could then. (in the 1930-1940) Many years later I discovered this means two parts of the light spectrum were corrected for convergence and a third part as best they could. Some time later Lithium Florided crystals were polished as a lens and it was shown that a greater part of the light spectrum would converge using this material. I am not a optics engineer, but using new glass, aspheric shaped lens all parts of the spectrum came to a focus, regardless of the color frequency. Fine telescopes first used this idea. ( for god's sake some engineer speak up and get me out of this hole) I first notices this when I purchases a 100mm APO f2.8. Those of you who use automatic focus cameras have forgot how hard it is to turn a knob and immediately come to the perfect focus. With the 100 apo lens the searching process with the knob is not so much a hit and miss proposition. You find the point very fast. With the 180 mm apo 3.4 this did not show up as much as the 100mm apo. I owned for a time the 280 mm apo 2.8 worked very fast also. I now have on order a 70-180 zoom apo. From reading this fine journal, I will look forward to receiving this fine article.. I just learned, that Leica is giving a $500 rebate an I took advantage when ordering. My favorite lenses are the 15mm, the28mmPC, the100mmAPO, 180mm APO 3.4, and believe the new zoom will join this lists. By the way, the longer the focus of the lens the better the correction or the more useful the APO glass is. I am sure an Optics man can better say it and I envite him or her to better vocalize this information. clifton (texworker@aol.com)