Archived posting to the Leica Users Group, 2007/01/07
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Jim, The laws of physics do not change and light of different wave lengths focuses at different points. Modern glasses help a lot in this especially if properly balanced with anomalous dispersion glass. But, and this is a big on, is that this only holds for a given set of wave lengths. Two extreme examples would be a lens that could focus X-rays not being the hot ticket for normal light and the lenses that are used in steppers. These are optimized for one frequency of light used to etch the lines on the chips. Totally useless outside of a very narrow wavelength of light. Let's go back to Brian's and Steve's images. Brian used a Noctilux which was a heavily compromised design to generate good imagery at F1 on film without using aspheric elements. For the use it was intended it is a masterpiece. It was never intended to do well with very long wavelengths of light. Moving on to Steve's images, they are much crisper and seem in better focus. Probably due to a much more modern design that handles longer wavelengths with more panache. Last, to pull a Ted; geesh guys, get a life. The new sensor handles light differently than we are used to. Non panchromatic films don't look the same, neither does Ektachrome look like Kodachrome. For most applications the M8 delivers an amazing wonderful image that is very sharp out of the box with out the built in sharpening from Nikon or the need to sharpen due to an aggressive anti-aliasing filter in Canon. Maybe I should buy three or four of these things and leave them in the box to fund my retirement ala a two lug M5 NOS or a black paint SP. :) Don don.dory@gmail.com On 1/7/07, Jim Nichols <jhnichols@bellsouth.net> wrote: > > 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 > > > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >