Archived posting to the Leica Users Group, 2011/03/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Nathan and Ted, The Zeiss ZM 50mm f1.5 C-Sonnar is well known to suffer from a pretty severe focus shift as you stop down. The point of sharpness moves back as you stop down. Zeiss originally sold them with the focus cam set so that focus, as seen through your camera's rangefinder, was correct when the lens was set at f2.8. At smaller apertures, depth of field was enough that the shift didn't keep the focused subject from being sharp, but at f1.5 and f2 the lens would front focus (quite a bit at f1.5). People complained that the lens wasn't sharp at f1.5, which is untrue. It IS sharp at f1.5, IF the lens is adjusted to be in focus at f1.5, so later ones were sold by Zeiss set for f1.5. This makes them unusable at smaller apertures till you stop down quite a bit, from what I've seen online. I know with mine, which is set for f2.8, the lens is not usable at f2 or f1.5, which does not bother me as I wanted it for portraits and I never do portraits wider than f2.8. Some of the people on rangefinderforum claim the lens is perfectly fine at f1.5 with one set for 2.8, you just have to 'lean in' a bit to compensate for the front focusing at wider apertures, but I hate guessing-games like that. I need stuff that 'just works' so I use it at the apertures it 'just works' at. F2.8 and below. To reiterate, the focus shift is real, despite what some of the know-it-alls online claim. For some reason some people think it makes them look smart to claim that focus shift in some lens designs is an 'internet delusion', despite Zeiss saying that the C-Sonnar does this, and despite the fact that testing it is not hard and shows the shift to be there. I have tested my lens extensively, and the shift is severe at f1.5 and at f2 its enough to make the photo still look too soft. This lens is capable of being VERY sharp when used correctly. I think mine is sharper in the senter at f2.8 than my 50mm tabbed Summicron, though the Summicron is a lot sharper in the corners at that aperture. Stopped down a couple more stops, they're equally good across the full frame. -- Chris Crawford Fine Art Photography Fort Wayne, Indiana 260-486-2581 http://www.chriscrawfordphoto.com My portfolio http://blog.chriscrawfordphoto.com My latest work! http://www.facebook.com/pages/Christopher-Crawford/48229272798 Become a fan on Facebook On 3/20/11 2:03 AM, "tedgrant at shaw.ca" <tedgrant at shaw.ca> wrote: > Nathan Wajsman ASKED? > Subject: Re: [Leica] New portrait of my son added today > > >> Nice portrait, but how do you know that a particular lens is optimized for >> a particular aperture?<<<< > > Hi Nathan, > You beat me to the very question? :-) > > Hi Chris, > How was this setting established? What kind of measurement method did you > use? Or who and how was it determined that f.2.8 was the optimum aperture? > > Thanks, > Dr. ted > > > >> On Mar 19, 2011, at 5:28 PM, Chris Crawford wrote: >> >>> http://tinyurl.com/mack30811 >>> >>> I shot this one a couple weeks ago with the 50mm C-Sonnar. Mine's >>> optimized >>> for f2.8, which is the aperture I used. >>> >>> >>> -- >>> Chris Crawford >>> Fine Art Photography >>> Fort Wayne, Indiana >>> 260-486-2581 >>> >>> http://www.chriscrawfordphoto.com My portfolio >>> >>> http://blog.chriscrawfordphoto.com My latest work! >>> >>> http://www.facebook.com/pages/Christopher-Crawford/48229272798 >>> Become a fan on Facebook >>> >>> >>> >>> _______________________________________________ >>> 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