Archived posting to the Leica Users Group, 2012/03/30
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Steve, If you want to wait until next week, I can tell you if NJ does a good job. I sent both my M and my Nocti back to have them "mated." Purportedly when I bought my M and Nocti from the dealer a few months ago, the dealer sent the Nocti to NJ to have it CLA'd and coded and "brought to specs" with their standard M9 (not mine). I think you know the rest of that part of the story. I will get both my M and Nocti back hopefully mid week next week and can let you know how it is by the weekend. Best, Bob On Fri, Mar 30, 2012 at 4:43 PM, Marty Deveney <benedenia at gmail.com> wrote: > On Sat, Mar 31, 2012 at 6:00 AM, Richard Man <richard at > richardmanphoto.com > >wrote: > > > I think the proper terms is back focus. > > > > "Back focus" gets used all over the internet for everything from out of > spec equipment to focus shift. Steve's lens is not adjusted to factory > specs. > > > > If the focus point changes as you change the aperture, then it's focus > > shift and you are stuck. You can then decide to calibrate to an aperture > > that makes the most sense to you, usually at wide open and hope the DoF > > will cover for any errors in narrower aperture. > > > > If you have genuine focus problems wide open the problem is not focus > shift. > > The focus point of the Noctilux shifts substantially when stopping down. > As Leica adjusts this lens when correctly focused the plane of optimum > sharpness for a Noctilux is slightly (very slightly) in front of the point > you focus on. Then as you stop down the focus point shifts back, mostly > within the plane of sharpness offered by increased depth of field. You can > get Leica to adjust the lens to focus correctly at f1 but then focus shift > means that your focus will be off until f5.6. I got mine adjusted this way > because I always carry an f2 50mm lens when I carry my Nocti, so it > basically gets used at f1 or not at all. > > Your lens and camera(s) need to be adjusted to factory specifications and > tested together. You need specialised equipment to do this. > > > > > I believe this is one of the reasons why the Nocti /0.95 was created. > > > > And because some of the special glass in the f1 ran out and more couldn't > easily be manufactured. > > > > You should test out whether it's focus shift. Just put the camera on a > > tripod and photograph a yard stick at an angle. Take multiple photos > > without changing the focus but only the aperture. > > > > This is good advice, but the first thing to do is to do some really > critical wide open focusing to see where the point of optimum sharpness is > relative to the focus point. If this is off, then there's no point > worrying about focus shift; you know it's there. > > Marty > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information > -- Bob Adler Redwood City, CA http://www.rgaphoto.com