Archived posting to the Leica Users Group, 2007/09/02
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I obsessed about this for a few weeks (esp with my noctilux) Then I let it go.. Certainly your camera should be in proper alignment, but to chase after each lens' focus shift will make you insane! I am learning to compensate (again, esp with my noctilux) for wide open near focus. The issue is focus shifts that none of us noticed prior to the advent of super thin image sensor surfaces. take pictrues have a cocktail Eric On 9/2/07, Leonard Taupier <len-1@comcast.net> wrote: > > Hi Hoppy, > > It is a global focus error on the Noctilux, 75 Summilux, and the > 90AA. In the case of the Noctilux there is also a focus shift at f2.0 > and f2.8. Without the adjustment it takes an f5.6 setting for the DOF > to bring it in focus. That is because the DOF increases quicker > behind the target then in front. The other lenses don't appear to > have the focus shift problem when stopping down. > > Cheers, > Len > > > On Sep 2, 2007, at 2:20 AM, G Hopkinson wrote: > > > Len, understood. You are describing a focus shift as you stop down > > slightly, rather than a global focus error requiring individual > > lens adjustment. Focus presumably correct wide open, shifts as you > > stop down owing to residual aberration. Error not apparent as you > > get to smaller apertures with greater DOF. Evidently your method > > works for you guys and that's what is important. Worth reading the > > article in the August LFI on the subject, if you get a chance. > > Thanks for the information. > > Cheers > > Hoppy > > > > -----Original Message----- > > Subject: Re: [Leica] Re: do it yourself back-focus adjustment..." > > > > Hoppy, > > > > The adjustment is the infinity adjustment cam just inside the camera > > mount. The close focus adjustment is actually behind the Red leica > > dot on the front of the camera. It's not a case of just adjusting DOF > > to be favoring in front or in the rear of the focus point. In the > > case of the Noctilux and the 75mm Summilux, from wide open to a stop > > or two closed all the photos are just plain out of focus. Between > > about 5 to 10 feet from the target, the only thing in focus was > > behind the target. I own 19 M lenses that I can use on my M8 and 5 > > LTM lenses I use with adapters. After my adjustment every lens > > focuses perfectly on the M8 except the 135mm at infinity. So I am not > > matching 1 lens to 1 body. I don't think the 24 lenses needed > > adjustment and the M8 didn't. BTW leica does not recommend using a > > 135mm on the M8. > > > > Len > > > > > > On Sep 1, 2007, at 7:15 PM, G Hopkinson wrote: > > > >> Guys can someone be explicit there regarding what you are > >> correcting? Focus wide open at practical infinity or a close > >> position? > >> Focus at a particular f stop? Someone said that they are adjusting > >> so that there is more apparent DOF in front than usual. Since > >> the acceptably sharp zone will always be deeper behind, I read this > >> as actually moving the sharpest point forward. > >> There is a difference between a global back focus (lens adjustment > >> error) and a focus shift visible near wide open as you stop down. > >> > >> I can certainly understand that you may end up with an adjustment > >> that works in practice for your own circumstance (lens and use), > >> I'm just really interested as it seems to me that you are > >> introducing new errors, especially with other lenses for example. > >> It may > >> be that DOF masks the error with other lenses. Just guessing, I > >> imagine that Leica is checking/adjusting the individual lens focus > >> mechanism, which is not the same as adjusting the camera body > >> roller arm naturally. > >> > >> The inquiring Hoppy wants to know. > >> > >> -----Original Message----- > >> Subject: [Leica] Re: do it yourself back-focus adjustment..." > >> > >> Vick, > >> > >> The original idea to do this came from the Leica Forum. Look there > >> if you want to find a more rigorous approach to the problem. > >> > >> Bob > >> > >> On Sep 1, 2007, at 4:33 AM, Vick Ko wrote: > >> > >>> Okay, now I understand. > >>> > >>> You are adjusting the RF arm. I anticipate that it only takes a > >>> very very > >>> small amount of adjustment. If the adjustment is large, then you > >>> will end > >>> up affecting the infinity alignment of the RF image. > >>> > >>> Congratulations on discovering this method. > >>> > >>> regards > >>> Vick > >>> > >>> -----Original Message----- > >>> From: Robert Rose [mailto:robert.rose@mac.com] > >>> Sent: Saturday, September 01, 2007 2:33 AM > >>> To: Leica Users Group > >>> Cc: vick.ko@sympatico.ca; Leonard J Kapner > >>> Subject: do it yourself back-focus adjustment..." > >>> > >>> Vick, > >>> > >>> We had a thread on this around March or so. I had posted some > >>> samples and > >>> how to do it at: > >>> > >>> http://gallery.leica-users.org/v/rjrose/focus/ > >>> > >>> Bob Rose > >>> > >> > >> > >> _______________________________________________ > >> 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 > > > > > > > > _______________________________________________ > > 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 >