Archived posting to the Leica Users Group, 2001/02/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Dans un courrier daté du 25/02/01 09:21:53 Paris, Madrid, mark@rabiner.cncoffice.com a écrit : << Austin Franklin wrote: > > I decided to find out what the REAL effects of a UV filter are on image > degradation. I arranged for an afternoon of test time at a high end optical > testing facility in Cambridge MA. > > I am bringing my Hasselblad 110/2 and Leica 75/1.4 with their respective > Hasselblad and Heliopan UV filters, and will obviously test them with and > without the UV filters. They suggested as tests, both MTF and resolution. > Center and out to the edges. I also want to test focus shift. > > If anyone has experience with doing such testing and has some CONSTRUCTIVE > input on the testing procedure, I welcome it. Those who think this is > silly, well, given that this only costs $175/hour, and one filter is near > $100, I think that if I find out filters are useless, it'll easily recoup my > money by selling all my image degrading UV filters. If I find out filters > do not degrade the image such that it is perceptible, well, then I won't > waste my time debating this subject, as I will have facts to back up my > conclusions, and that will be well worth the effort and expense. > > I will publish the raw test results, no matter what they are. I fully > expect this to be quite controversial, and I also fully expect to find there > is 'some' degradation. It is the significance of the degradation that will > have to be 'analyzed' in order to draw any 'reasonable' conclusion to > whether a UV filter does actually degrade the resultant image. We can all try to argue over the relative merits of number systems and graphs and try to determine who really understands these systems and who really does not. I'd suggest after this high tech test a simple practical usage test. Aim the camera with a tripod at something. Take a shot, take the UV filter off take another shot. Aim the camera at something else, perhaps backlit this time take a shot, take the UV filter off take another shot. Continue until the roll is finished Have the transparencies run. Place them directly next to each other. Determine with ones own eyes if there is a discernible difference between the shots… and how many, and how much. If the difference is such that it makes you change your technique than do so, if not don't. Explain to the list perhaps your conclusions and if you feel you've learned anything, if you got results you didn't expect to get. Back to Katie Holmes on Saturday Night live. Mark rabiner >> Hey guys , looks like the heat is on , again ! NO FEAR JO GOODTIMES -FRANCE/ AIRBORNE RADAR TECH / LIVE FREE OR DIE