Archived posting to the Leica Users Group, 2006/06/17
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I presume that it is because they are using a lower mag viewfinder, just like the 135mm not being usable on the 0.58 RF. As the magnification goes down, RF accuracy goes down. The eyes on the 2.8 increase magnification, and therefore focusing accuracy. The resale value of the 135mm Elmarits with eyes may go up! Actually, if you read Erwin's article on RF focusing accuracy, the most difficult for the rangefinder to focus are the 135mm's. The longer focal length causes more focusing problems than the high maximum aperture. The article is pretty technical, but basically the RF baselength compared to the focusing distance makes middle- distances to be the most challenging. Accurately focusing the 135mm at 20 feet or so is more difficult than accurately focusing a Noctilux or 75mm Summilux at 1M. The rangefinder is extremely accurate at close distances, and loses accuracy as distance increases. This apparently is more of an issue than the maximum aperture reducing the DOF. Tom Schofield On Jun 17, 2006, at 5:43 AM, Don Dory wrote: > > I am still at a loss as to why the 135 APO can not be adapted but > the 135 > F2.8 can. The spectacles would help with focusing accuracy, but > they can do > the 75 Summilux which has an even narrower dof so it doesn't have > anything > to do with the rangefinder. The lens itself has the optics well > forward of > the mount so it is already teleocentric. > > Don > don.dory@gmail.com