Archived posting to the Leica Users Group, 1996/05/27
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 11:19 AM 5/27/96 -0600, you wrote: >You are probably talking nonsense. How can more glass give you better >results? The optical functions of the two lenses convolve with each other >and the result must be worse on strictly technical grounds. However, your >results may look more interesting and I will buy that. May be by putting the >converter on the Tamron, you injected some of that poorly quantified Leica >three-dimensionality into your negatives. I will buy that. > >I am afraid that your "tests" would not meet scientific criteria. You didn't address the reason why I think it works, and I realize I didn't make it real clear. The best part of a lens is in the center. A converter takes only the central portion of the lens's "cone of light" and multiplies its magnification. Thus, you're taking the best part of the lens's performance. The 1.4 Apo converter is so good (5 of the 7 elements are the famous "continue" glass) that there is no degradation of the image, compared to the Tamron by itself with the added unsharpness of the edges of the original lenses added into the mix. Just like when you stop down performance increases. If you have seen the tests of Leica's apo converters, and how little they actually degrade the image when used with Leica's lenses, or Canon's or Nikon's best converters, it's possible that their performance is so good that it will work as I described. On the other hand, maybe we had a Tamron lens that had a problem with performance at the edges, and this was a one of a kind phenomenon. Who knows? The other thing is, my co-workers noticed it too. And when we put the Tamron 1.4 converter on it, it was horrible! ========================== Eric Welch Grants Pass Daily Courier