Summicron 2.0/35: focus shift on M9 ?

[CK52X]

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Hello !

 

There are quite a lot of threads in this forum dealing with a possible (aperture dependent) focus shift when using the Summilux 1.4/35 asp. lens.

 

Does anybody know whether this issue does also concern the aspheric Summicron ?

Do the older (non-aspheric) versions of these lenses have this problem, too ?

 

Many thanks for any answer.

[jaapv]

There are some reports of this, but in real life - not in my experience.

[lars_bergquist]

All spherical lenses exhibit focus shift when stopped down. Law of nature. With small diameter (= slow) lenses, this falls below our horizon of perception. But it is there.

 

The only ways I know of (I am not an optical expert) that can remedy this are:

 

• an all-aspherical lens design (not likely, for economical reasons);

 

• as an approximation of the above, a lens with two aspherical surfaces, one in the front and one in the rear half, both probably large enough to make precision grinding necessary. Also very expensive; or ...

 

• ... a floating element or group. This was the solution chosen for the 50mm Summilux ASPH, its sibling the 75mm Summicron ASPH and of course the new Noctilux. Also a complication but maybe easier to master than the alternatives.

 

Most people sem to think that the upcoming new 35mm Summilux ASPH will have a floating element, as the elimination of focus shift must be high on the agenda.

 

The old man from the Spherical Age

[pklein]

I see it with my 35/2 Summicron v.4. Slight front focus at f/2, accurate at f/2.8 and smaller. The front focus is most noticeable close-up.

[luigi bertolotti]

When I got my Summicron 35 asph made a specific test with the usual focus chart, 45°, at 1,5 and 2 meters (a bit more than 2, indeed) : not appreciable shift at all, even if at 2,8 the "transition to OOF" looked a bit asymmetrical ... at 3 meters and more the DOF preavails... unuseful to test. My Summicron un-asph, which I tested for the first time in the same occasion, shifted rather significantly... but is a very first version of 1960...

[lars_bergquist]

In film days (upper Neolithic) focus shift was not much of a problem, because it could be held to a level so low that the depth of the film emulsion took care of it. An electronic sensor does not have any depth at all. We have entered an age when new criteria apply. The remarkable thing is that most older Leica lenses are still very useful. This says something about the quality level that the Leitz company worked to.

 

The old man from the Spherical Age

[250swb]

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My Summicron Asph front focuses a fraction until around f4, but only at test chart type distances does it matter (and for close up work a rangefinder isn't the ideal camera anyway).

 

Aperture related focus shift affects many lenses, its in the design (even if unwanted), and it can't be adjusted out with rangefinder tweaking or lens shimming, you only move it elsewhere in the focus scale. Its the thing that should really be tested for first before any judgement is made on whether a rangefinder is out of adjustment and sent off to Leica for re-calibration.

 

Steve

[pascal_meheut]

My 35/2 ASPH is spot-on on the M9. We tested it as well as another sample on a DxO chart using their analysis software and it does not exhibit any sign of focus-shift.

[adan]

for close up work a rangefinder isn't the ideal camera anyway

Steve

 

I disagree. I prefer RFs precisely because their relative quiet, and compact form, make them far less "aggresive" than an SLR in close, intimate quarters. They also hide my face from my subjects less. (right-eyed shooter). Amazing how I can disappear from my subjects' conciousness even at 2.5 feet away.

 

In fact, I just traded a pre-ASPH Summilux 35mm for a 35 'cron ASPH, precisely because it has a close-focus limit of 1 meter, and I just kept hitting that "wall" far too often.

 

My new 'cron, BTW, does not show any focus shift. But it should be noted that the '35 cron ASPH has a very flat field, which means that focus/recompose will always lead to missed focus at wider apertures - unless one accounts for it (see diagram).

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[250swb]

Yes Andy, I said close up (closest minimum focus distance) in context of talking about test charts. Close quarters is of course something else and I quite agree with you.

 

Steve

[likalar]

Adan,

 

Thanks for the great illustration.....worth a thousand words.

Larry