Archived posting to the Leica Users Group, 2008/12/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]On Dec 14, 2008, at 5:14 PM, Marty Deveney wrote: > > Len wrote: >> The two lenses that I have that have a definite focus shift are >> the Noctilux and the 75mm Summilux. > > Apologies if I jumped too fast, but there is some incredible garbage > being promulgated on the web about focus shift. > > The f1 Noctilux and the 75 Summilux definitely display the most > focus shift Marty, is this simply due to the fact that with their potentially very narrow dof they will show any focus shift most readily ? Steve > of the Leica lenses designed after 1970 or so (I haven't tested many > earlier lenses, but they tend to be more conservative designs so > they may not show much shift). As they left the factory, the 75s > were adjusted to have a tiny amount of front focus at f/1.4. As you > stop down, the focus shifts backward but within the depth of field. > If you adjust for perfect focus at f/1.4, your lens will focus > incorrectly until depth of field catches up at f/8. Erwin describes > the behaviour of the Noctilux and its focus shift here: > http://www.imx.nl/photo/leica/lenses/lenses/page56.html > > Dante Stella gives a good explanation about why adjusting the > rangefinder in your camera to 'fix' focus shift is hazardous: > http://www.dantestella.com/technical/leicadjust.html if you have a > range of fast lenses, don't even think about it. > > My 35/1.4 ASPH tended to focus behind the point of focus when I > first put it on my M8. A trip to Leica fixed that. It displays > remarkably little focus shift considering the design - perhaps Leica > will redesign all their lenses to include a floating element at some > stage. > > Marty > > Gallery: http://gallery.leica-users.org/v/freakscene > > > -- > Be Yourself @ mail.com! > Choose From 200+ Email Addresses > Get a Free Account at www.mail.com > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information