[Leica] Received M8 & lenses repaired/adjusted by Solms

[robertmeier at usjet.net (Robert Meier)]

Peter,

Does this focus-shift problem occur with R lenses on the DMR?

Robert

On Jun 29, 2010, at 1:09 PM, Peter Klein wrote:

> Peter:  I know what you're going through. Leica should make good on  
> your
> problems, but the issues are complex, and some real-world  
> compromises may
> be needed.  Let me give you an overview of the situation.
>
> Those of us experienced with film Ms tend to think of the Leica
> rangefinder as a perfect device. And with film, for all practical
> purposes, it was when properly adjusted. Nobody complained about focus
> shift and back/front focus except with the Noctilux.
>
> The digital Ms have much greater precision requirements for  
> focusing, due
> to the fact that the image-making plane on a sensor is a flat plane,
> whereas film has thickness.  And the M8's lack of an anti-aliasing  
> filter
> means that you really see minute differences in focus accuracy.   
> When the
> M8 came out, Leica was still adjusting lenses to film-M specs, which
> wasn't good enough. Supposedly they've upgraded their equipment and
> testing procedures.  But there are enough stories like yours that I
> wonder.
>
> DAG (Don Goldberg) in Wisconsin is the only person on the planet  
> that I
> know of outside Leica itself who can truly optimize lenses for the  
> M8. He
> will adjust your lenses using a known-good M8.  If necessary, you  
> can send
> him both your M8 and your lenses, and he will make sure both are up to
> standard.  With Don, it may take a while, but you know he will get  
> things
> as right as they can be.  With Leica, it seems to be a crapshoot.
>
> 90mm lenses and very fast lenses are the hardest to get right. With  
> some
> fast lenses, you have a choice.  You can have a lens adjusted to focus
> perfectly wide-open, in which case it will back focus at middle  
> apertures;
> or you can have it adjusted so they are perfect from f/2.8 and  
> narrower,
> in which case they will front focus wide-open.  I had DAG adjust my  
> 35/2
> pre-asph Summicron IV in the latter manner, since I mostly use it
> outdoors.
>
> My 35/1.4 Summilux ASPH came from the factory optimized for wide- 
> open use.
>  It back focuses slightly at middle apertures, but I know what to  
> do to
> get it right--focus on a person's nose instead of their eyes, or  
> focus on
> the closest thing I want in the zone of focus rather than the  
> middle of
> the zone. Since it's behaving exactly how Leica described it in a  
> Leica
> Fotographie article, I decided to leave it alone. I hand-code it  
> rather
> than send it to Leica, and risk an experience like yours. If it  
> ever gets
> out of adjustment, I'll send it to DAG.
>
> Even DAG was not able to get my pre-Asph 90 Summicron to focus  
> perfectly.
> But he got it close enough and consistent enough that I know what  
> to do to
> compensate when I use it in the theatre or concert hall. My old  
> 1960s 90
> Elmarit is hopeless on the M8, and it was fine on film.  My other  
> 90 is a
> Voigtlander 90/3.5 Lanthar, and it is perfect at all stops--so this  
> is the
> 90 I use the most. Even Leica has admitted that faster 90mm lenses  
> may be
> beyond the accuracy of the rangefinder system on the M8.
>
> Now the dirty little secret: All fast lenses have focus shift. It's  
> always
> been there, but we never noticed it on film.  With the M8, the  
> question is
> how much and whether it really matters. I can detect it on my  
> tabbed 50
> Summicron, but it doesn't really matter in practice. My 50 Dual-Range
> Summicron (altered to mount on the M8) has so little that it can be
> ignored. A lens like the VC 35/1.4 Nokton has a great deal of focus  
> shift,
> and it's never going to be perfect at all stops and distances.
>
> This is one reason why Leica is creating new lenses with floating  
> elements
> (like the new 35 and 50 Summilux ASPH lenses).  Voigtlander solved the
> focus shift problem on the big 35/1.2 Nokton by not correcting some
> aberrations, such that as you stop down, the focus shift actually
> oscillates back and forth slightly across the point the rangefinder is
> actually focused on. I've reproduced this myself, and couldn't  
> believe my
> eyes. Erwin Puts told me that no, I wasn't imagining it, it was  
> part of
> the lens design. The result is a lens that is for practical  
> purposes, free
> of noticeable focus shift. The price you pay is in contrast.
>
> So, getting lenses to focus correctly on the M8 is a complex  
> process with
> several variables:
>
> 1. Is your M8 exactly up to standard?
> 2. Is your lens exactly up to standard? (if either of these two  
> factors
> are off, you will have front or back focus at all stops. If the  
> camera or
> the lens cam is way off, you may have correct focus at some  
> distances and
> not at others).
> 3. How much focus shift does your lens have?  If focus shift is a
> practical problem, then...
> 4. Do you want your lens optimized for wide open, middle stops, or  
> some
> compromise where it's almost right everywhere, but not quite? If the
> compromise is sufficient for the kind of photography you do, great. If
> not, pick the optimization you want. Compensate when needed, or use
> different lenses for available light vs. outdoors.
>
> I hope this is helpful.
>
> --Peter
>
>
>
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