Archived posting to the Leica Users Group, 2007/10/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Dear Len, How about the 28mm setting on the TriElmar? I have shot many IR photos using this lens and did not notice the hotspot phenomena you experienced with the Summicron. Cheers Howard. On 13 Oct 2007, at 9:06 AM, lug-request@leica-users.org wrote: > Date: Fri, 12 Oct 2007 20:51:42 -0400 > From: Leonard Taupier <len-1@comcast.net> > Subject: Re: [Leica] George: 28mm Summicron IR problem > To: Leica Users Group <lug@leica-users.org> > > In addition to the sensitivity of the sensor the quality of digtal > infrared depends on the characteristic of the lens. > > For example, the Canon EF-S 18-55mm f/3.5-5.6 typically produces a > pronounced hot spot as can be seen in the sample picture to the left. > The hot spot is a a result of internal reflections within the lens > produced by the lens' coatings. Some types of coating are not > transparent to near-infrared wavelengths. > > The above was taken from a web site dedicated to Infra Red digital > photography. Quite a few lenses are listed which produce these hot > spots. The author did not include Leica lenses in the recommended or > hot spot producing lists. > > Len >