Archived posting to the Leica Users Group, 2015/09/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]For infrared, most lenses should respond to close focusing the lens such that the barrel is extended 1/200 of the focal length. Put the lens at infinity. Measure the whole length with a caliper. Focus closer to extend the lens (so 1/4mm for a 50mm lens). You can place your IR mark where infinity is. This will not work with IF lenses. Dante > On Sep 10, 2015, at 6:56 PM, Jim Nichols <jhnichols at lighttube.net> > wrote: > > Ken, > Thanks. I reviewed the list. > > Jim Nichols > Tullahoma, TN USA > >> On 9/10/2015 5:47 PM, Ken Carney wrote: >> Jim, >> >> If a lens is vulnerable to a hot spot, it gets worse as the lens is >> stopped down. Kolari >> (http://kolarivision.com/articles/lens-hotspot-list/) says that your Fuji >> 27mm is only useable at 2.8, which is probably OK anyway since you'll >> need all the light you can get. Based on my experience with other Fuji >> lenses, I'm confident that auto focus will be fine. With your Leica >> lens, you can just magnify and focus through the EVF. >> >> Ken >> >>> On 9/10/2015 4:20 PM, Jim Nichols wrote: >>> In my mind, the "hot spots" have no direct connection to focusing, >>> unless, in their effort to get the total image focused in one plane, >>> they have created the hot spot much as one does with a simple magnifying >>> glass. It could be an unexpected result of their pursuit of perfection. >>> But, I could be totally off-base here. >>> >>> Jim Nichols >>> Tullahoma, TN USA >>> >>>> On 9/10/2015 4:04 PM, George Lottermoser wrote: >>>>> On Sep 10, 2015, at 3:53 PM, Jim Nichols wrote: >>>>> >>>>> What I have read this afternoon indicates that the latest Leica lenses >>>>> are focus-corrected to such high wavelengths that, for all intents and >>>>> purposes, no further correction is required. Having no intention of >>>>> making such an investment any time soon, I did not spend a lot of time >>>>> following this back to its source. >>>>> >>>>> Another slant on this was that Leica removed the IR index because it >>>>> confused their customers, and that it is really only valid at >>>>> infinity, anyway. And, with zoom lenses, there are multiple >>>>> correction settings depending on where the lens is in the zoom range. >>>>> >>>>> Most folks seem to feel that some experimenting is necessary to find >>>>> the most useful setting for the type of photography intended to be >>>>> carried out. >>>> Interesting. >>>> >>>> Though my experience with the 093 IR filter from B+W >>>> contradicts the claim; >>>> at least for the 28 Summicron, 50 Summilux Asp, and 35 Summilux Asph. >>>> Perhaps these are no longer considered the "latest Leica lenses." >>>> Even if they did focus correctly; >>>> they still all produce the significant hot spots; >>>> and ever more prominently as you stop down. >>>> >>>> And yes the proof is, as always, in the YMMV pudding. >>>> >>>> Regards, >>>> George Lottermoser >>>> >>>> http://www.imagist.com >>>> http://www.imagist.com/blog >>>> http://www.linkedin.com/in/imagist >>>> >>>> >>>> _______________________________________________ >>>> 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