Archived posting to the Leica Users Group, 2008/12/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 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