Archived posting to the Leica Users Group, 2008/01/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]As I heard it years ago from a Leica Rep., Leica uses the term very conservatively, requiring that apo correction exist at all apertures and focusing distances (and focal lengths for zooms), unlike some after-market Cos. which use "apo" if that correction exists at an optimum aperture and distance. In fact, they are so highly corrected that infrared photography with them does not require refocusing -- i.e. they are corrected all the way into the infrared. Tom On Jan 5, 2008, at 5:37 PM, Henning Wulff wrote: > At 10:15 AM -0800 1/5/08, wildlightphoto@earthlink.net wrote: >> Raimo K <raimo.m.korhonen@uusikaupunki.fi> >> >>> Since when do they use this designation? >> >> Since 1984 at least if not earlier. >> >> Doug Herr >> Sacramento >> http://www.wildlightphoto.com >> >>> >>> ----- Original Message ----- >>> From: <wildlightphoto@earthlink.net> >>> To: "Leica Users Group" <lug@leica-users.org> >>> Sent: Saturday, January 05, 2008 3:17 PM >>> Subject: Re: [Leica] The Tele elmarit 135 Is So A Real Pooch of a >>> Lens >>> >>> >>>> Raimo K <raimo.m.korhonen@uusikaupunki.fi> wrote: >>>> >>>>> APO means apochromatic correction of the lens, there are no >>>>> apochromatic >>>>> elements. >>>> >>>> In Leica's case, APO is the designation they use for the extra-low >>>> dispersion glass which their optical designers feel is >>>> essential to >>>> designing lenses with apochromatic performance. This is like >>>> Nikon's use >>>> of the ED designation for their extra-low dispersion glass. >>>> Raimo is >>>> correct that there are no apochromatic elements, but there is >>>> APO glass >>>> which is used to design apochromatic lenses. >>>> > > > In Leica's case they also use the term correctly. They use the APO > designation to indicate apochromatic correction. Yes, in many cases > special low dispersion glasses can help to achieve this, but low > dispersion or anomalous dispersion glass is not essential for > apochromatic correction. > > Leica uses low dispersion glasses on various non-apochromatic > lenses as well. > > -- > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw@archiphoto.com > |[ ]| http://www.archiphoto.com > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information