Archived posting to the Leica Users Group, 2001/02/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Here's why I don't like optical bench testing of UV filters. Lets say you test a lens with a filter and you get a test value of 7.9 (with filter) and 9.2 (without a filter) In whatever units you are measuring on the optical bench. You may conclude that without a filter you get a value 1.3 more than with and therefore you shouldn't use UV filters to protect a lens. But, what means 1.3? Can this be seen in an 8x10 print? 11x14? 24x36? What are the minimum test value differences before a certain enlargement size at a certain viewing distance becomes visible to the human eye? People go to Photodo.com and compare lenses using their weighted average statistic. A lens with a value of 92 is clearly better than one with a value of 89, or is it? What do any of these numbers mean? One thing is for absolute certain. When you (Austin) do the testing, you WILL find a difference. There's ALWAYS a difference, even when you make two tests of the same lens. The question is, "how are you going to interpret these differences?" dan c.