Archived posting to the Leica Users Group, 2007/09/30
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I just ran the experiment myself with M8, 'Lux 50 asph, and IR filter. I duplicated Len's result, but our reflection is not the same as Howard's in that Len and I got a distorted reflection of the flashlight's lens, not round but crescentic. Howard's reflected sign was an apparently linear reflection and without magnification or minification. I think that Len's and my result comes from a reflection of the flashlight from a curved surface somewhere inside the lens (note the green cast, many stops fainter than the primary image of the flashlight, as would be seen in a coated optic) in turn reflecting off the filter and imaged as such by the lens; in other words, the camera is seeing (by reflection) in the filter a reflection from the camera's lens. I did not get this reflection with the filter off. Phil's reflections are similar but not the same. They are located between the direct image and the center of the frame, not diametrically opposite the center like all the other reflections we've been looking at. This indicates that they are reflections in the filter of reflections from the coated (green cast) front surface of the lens. (Look different because different lens.) Neither of the above explains Howard's reversed and linear reflection, indicating reflection from plane surfaces, which don't mag/minify and which don't reverse and invert images if they are parallel. Neither can I. Also, Howard's reflection was bright enough to be seen against a background that was not black but merely gray, and was of a primary image that was not densely overexposed as were my and Len's flashlights. I don't think this phenomenon arises within the lens/filter system. I wonder if it's even optical at all. Could it be some kind of anomalous electronic effect having to do with an "echo", reverse- order readout of residual charge or some such on the CCD? Howard, are you having us on? ;-) If so, please wait for April 1st. If not, please try these things: First, repeat the photo as exactly as possible, both with and without the filter. Then, using the same lens and filter (you may use a different camera...!), shoot the same scene on film. Finally, if you see the effect again in the M8 but not on film, repeat the whole thing when you get your own M8 back. My prediction is that, if it persists in the first M8, it won't be duplicated in the new one. Show us the results. --howard On Sep 30, 2007, at 1:39 PM, Philippe Amard wrote: > I attribute it to the filter - but not sure - same problem with L1 > and Leica D Vario. > So I'd say it is not linked to either, IR, specific lens or M8. > Look at the two green dots. > http://perso.numericable.fr/phamard//GAL-Albi-2oo7-Cathedrale/ > content/20070715_P1010439_large.html > > Yours > Phil...x