Archived posting to the Leica Users Group, 2007/01/07
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Adam, I went back and reviewed the Noctilux data that Brian posted earlier today. There does not appear to be a separate "R" index on the Noctilux for use in infrared photography. I recall being told some time ago that the separate index was no longer needed on recent Leica lenses because the color correction has improved to the point that IR is rendered properly when using the normal focusing index. If this is true, then one should be able to focus properly using visible light, regardless of the nature of the light source. Maybe someone can elaborate on this. Jim Nichols Tullahoma, TN USA ----- Original Message ----- From: "Adam Bridge" <abridge@gmail.com> To: "Leica Users Group" <lug@leica-users.org> Sent: Sunday, January 07, 2007 12:32 PM Subject: Re: [Leica] A tripod, an M8, and two candles - do some science > If infra red is really a prime illuminate in the image then the focus > will be shifted because of the substantially longer wavelengths of the > IR. So you'd expect the focus to be "off" - if it weren't I'd be > thinking IR wasn't an issue. > > I'd like to see some rigorous science done here - creating a > thoughtful series of controlled experiments to explore what is being > observed and determine the meaning. > > Adam > > > On 1/7/07, Jim Nichols <jhnichols@bellsouth.net> wrote: >> Brian, >> >> I don't wish to get into the definition of depth of field or allowable >> circles of confusion. However, if you go to the full size image in the >> second photo, you will notice that the highlights on the rim of the neck >> of >> the oil candle are not nearly as sharp as the highlights on the frame in >> the >> background. This is what led me to state that the sharpest focus is >> behind >> the candle flame. >> >> Jim Nichols >> Tullahoma, TN USA >> ----- Original Message ----- >> From: "Brian Reid" <reid@mejac.palo-alto.ca.us> >> To: "Leica Users Group" <lug@leica-users.org> >> Sent: Sunday, January 07, 2007 11:49 AM >> Subject: Re: [Leica] A tripod, an M8, and two candles >> >> >> > >> >> I am assuming that you were careful not to change the focus between >> >> the >> >> two shots. >> > >> > Correct. >> > >> >> I notice in the second shot that the frame in the background seems to >> >> be >> >> the plane in focus. The IR effects are interesting, but I do not >> >> think >> >> that you have eliminated the focus question. >> > >> > According to the manual that came with the Noctilux, the depth of field >> > at >> > f/5.6 at that distance (1.5 meters) is about 22cm. I believe I have >> > eliminated the focus question. >> > >> > (http://www.leica-camera.us/assets/file/download.php?filename=file_153.pdf, >> > page 6) >> > >> > >> > >> > _______________________________________________ >> > Leica Users Group. >> > See http://leica-users.org/mailman/listinfo/lug for more information >> > >> >> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information >> > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >