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

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Subject: [Leica] retro focus…
From: sonc.hegr at gmail.com (Sonny Carter)
Date: Sat, 31 Mar 2012 07:31:37 -0500
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> <CB84B9B5-A7B1-4531-986A-9DAD67E52B32@gmail.com>

Over the years, since I started with the M8 and now with the M9, I've found
four lenses that worked OK with film that needed "tightening up" focus wise.
I sent them all to DAG and with the exception of the C/V 28/1.9 that he
says he could not adjust, I've been really happy with the result.  I did
not send the camera.

When I was in TV news, we routinely sent new Angenieux zoom lenses for
collimation on CP16 cameras.





On Sat, Mar 31, 2012 at 3:53 AM, Steve Barbour <steve.barbour at 
gmail.com>wrote:

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



-- 
Regards,

Sonny
http://sonc.com/look/
http://sonc-hegr.tumblr.com/
Natchitoches, Louisiana

USA


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…)
Message from steve.barbour at gmail.com (Steve Barbour) ([Leica] retro focus…)