Archived posting to the Leica Users Group, 2012/03/31

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: [Leica] retro focus…
From: steve.barbour at gmail.com (Steve Barbour)
Date: Sat, 31 Mar 2012 01:53:52 -0700
References: <0AA0D6C6-986B-48D5-9DB8-DD9E4A7F142E@gmail.com> <CAF8hL-Fy3mz82+wFFKL9LiCTCRXcAQ587OQ7YbPoHB+3zCvP-w@mail.gmail.com> <CABmfTOWduEWDHXhKPHTBme48JUn=biCRK-P1RCXck+=Es=mb2Q@mail.gmail.com> <CAAsXt4M7JT=YX+S6Jp64sjuSbN8Uog6NiXebVo3AMiuBnP-n_w@mail.gmail.com>

On Mar 30, 2012, at 6:34 PM, Robert Adler wrote:

> 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.


I think I will wait to hear from you Bob,


thanks, Steve


> 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
> 
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information



Replies: Reply from sonc.hegr at gmail.com (Sonny Carter) ([Leica] retro focus…)
In reply to: Message from steve.barbour at gmail.com (Steve Barbour) ([Leica] retro focus…)
Message from richard at richardmanphoto.com (Richard Man) ([Leica] retro focus…)
Message from benedenia at gmail.com (Marty Deveney) ([Leica] retro focus…)
Message from rgacpa at gmail.com (Robert Adler) ([Leica] retro focus…)