Archived posting to the Leica Users Group, 2007/08/30
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Bob, I looked again and Chelsea is still cute. I have a couple of dogs rather impatient when the food bowl comes out, as well. I'm with you too on the very narrow DOF wide open. Maybe of interest to sum up some points from that LFI article for LUGgers that don't subscribe. These are from statements by the article's author: Most fast lenses of any make will exhibit some focus shift. The M mount 50 asph and 75 asph do not, due to their floating element and asph design. (on that point, I tested my 50 carefully and could detect zero error at 1 meter and effective infinity at 1.4 & f2 vs stopped down) The article names the 35 1.4 asph, the 75 1.4 and the Nocti as most often mentioned. The effect is masked by greater DOF once the lens is stopped down. The shift is more noticeable with sensor capture rather than film, both because of the nature of the sensor and also examination at 100% of the files on computer monitors (equivalent to a very large print). People are much more aware of the effect due to the nature of internet information sharing. Accurate focus is made more difficult by the lower magnification of the M8. They suggest the 1.25 magnifier attachment for use with 50 and above. Leica is receiving record numbers of lenses for adjustment. It is possible to tune the designs for less emphasis on wide open performance. Leica's emphasis is on the best possible wide open performance. Zeiss claims that their ZM designs exhibit minimal focus shift. Most of those are not fast lenses. Cheers Hoppy -----Original Message----- From: lug-bounces+hoppyman=bigpond.net.au@leica-users.org [mailto:lug-bounces+hoppyman=bigpond.net.au@leica-users.org] On Behalf Of Robert D. Baron Sent: Friday, 31 August 2007 09:46 To: lug@leica-users.org Subject: Re: [Leica] IMG: Chelsea At The Door On August 28, 2007, Hoppy wrote: > Bob, a nice warm pet portrait. Thanks, Hoppy, and others who wrote. It was late afternoon / early evening sun, which gave the photo a nice warm light....Chelsea (who was waiting to go in for supper) is a smart, affectionate and occasionally very hard headed dog, who waits for no man when the food is being dished out... > The back focus issue is a very interesting one. There is an article in the > current (August) LFI which discusses the issue at some > length. Leica reports record numbers of lenses being sent for adjustment. > The most vulnerable being basically the -luxes. Clearly > any error would be most apparent with the very fast lenses. However they > have said that the later design of the 50 asph and 75 asph > with floating element is meant to be less vulnerable and this may be their > future basis for lens designs of that type. Leica > suggests that errors that may have been present with film cameras too are > perhaps more noticeable with digital capture. Especially > now that there is a greater awareness of the issue. > Thanks. I just read the article. I don't pretend to understand everything I read but I guess it makes sense insofar as I do. > I like their one line solution if you get a focus shift. Just shoot the > lens > wide open all the time! A little impractical with the 75 Summilux, which at 1.4 and close in has depth of field about equal to the width of a human (or dog) hair. The shot of Chelsea was at 2.8 or 4.0 (ISO 320) and cropped a bit; I was standing maybe 8 or 10 feet from her. The depth of field is minuscule here and at 1.4 it would have been almost non-existent. I love the images this lens produces when I hit the focus, but often times luck plays a large role. > > Cheers > Hoppy Regards, --Bob > > -----Original Message----- > Subject: [Leica] IMG: Chelsea At The Door > > Here is a shot made this evening with my M8 and 75mm Summilux of > Chelsea, one of our older Cavaliers (she is ten) at the back door. > > The 75 just came back from Leica New Jersey, along with my 35mm ASPH > Summilux and 50mm pre-ASPH Summilux. I had back-focus issues with these > three lenses on my M8 so I sent them in to Robert Fisk and his > technicians for 6 bit coding and focus calibration. > > I think they did a great job. > > My Noctilux goes in tomorrow. > > http://www.bobbaron.com/W_L1002843ChelDoor.jpg > > --Bob _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information