focus shift on 35 Lux

[shootinglulu]

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I have been told that there are focus shift problems with the 35 Lux asph on the M8 but not the M8.2 and that because of this, i will have problems on my M8... Can anyone tell me if this is true, a real shame if it is.

I was also told (by a Leica dealer) that Leica have told him they are not bringing out a new 35 Lux.

Thanks

Lucy

[carstenw]

The focus shift is inherent in each lens, and has nothing to do with the body. It will appear on M8, M8.2 and M9. Some copies of this lens don't focus shift, or do so only minimally, others are worse. Test before buying.

[shootinglulu]

Thanks.

The man told me the focus shift was worse in older model m8's, which i think mine is and i got a little worried.

[Nicoleica]

Thanks.

The man told me the focus shift was worse in older model m8's, which i think mine is and i got a little worried.

 

Was this gentleman a salesman by any chance? It sounds awfully like an attempt to persuade you buy a new camera.

[carstenw]

The man told me the focus shift was worse in older model m8's, which i think mine is and i got a little worried.

 

That is plain wrong, I don't know how else to say it. The closest I can come to guessing at why he might have said that in an honest fashion is that he tested an M8 which wasn't as well adjusted to the lens as the M8.2 he tested.

 

In general it is possible to mitigate the severity of a focus shift by setting the wide open focus near the front of the DoF, and let the rearward-moving focus shift move backwards in the field as you stop down (or the other way around if I remember it backwards).

 

It is possible that the M8.2 was (coincidentally) adjusted like this, and the M8 not.

[shootinglulu]

Hi Nicole.It does sound a bit like that, but i don't think so. I think that's what he thought.

 

Carsten, thankyou for that. I trusted your view as the correct one.

Lucy

[jsouteyrat]

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Hi

I have focus shift with my M8.2...

Focus is good at 1,4 and from 5,6 to 16.

 

Hope it will help.

[carstenw]

It is possible that a tiny tweak of the focus wheel with a 2mm hex key will improve on that slightly. I don't know if you are into experimentation of that nature, but others have reported success. I have tweaked the wheel myself, but not for my 35 Lux ASPH, which appears to have only very mild focus shift, within the depth of field.

[shootinglulu]

That does help as i tend to shoot wide open.

Looks like i'll have to wait a while though as Leica have them on back order.

Thanks

Lucy

[carstenw]

Do test before buying though. If you should ever decide to sell it again, it will hold its value better if the focus shift is not large.

[lars_bergquist]

The entire subject of the focus shift of the 35 'lux ASPH has been beaten to death at least twice in this forum. The shift exists; it may be more or less noticeable with different specimens because of minute differences in the factory focus adjustment, or because the owner is a more or less fanatical pixel peeper, but definitely NOT because of exterior finish. It is true that a digital sensor can show up minimal shifts of focus in a clearer way than film can, however. This, expressed in the most direct and brutal way, is because a silicon sensor is sharper than a piece of film.

 

This said, my own specimen which seems to be about average, gives me no problem at all with real-life three-dimensional subjects at normal shooting distances. The pictures come out just fine. To quote the immortal Alfred E. Neuman: "Who, me worry?"

 

The old man from the Age of Film

[Guest mc_k]

In general it is possible to mitigate the severity of a focus shift by setting the wide open focus near the front of the DoF, and let the rearward-moving focus shift move backwards in the field as you stop down

 

can be done by a physical adjustment at Leica, or by giving the focus ring a little bump in the appropriate direction when you are stopped down.

[D&A]

In my opinion along with moderately extensive experience with a number of Leica 35mm f1.4 ASPH lenses, Lars is exactly correct in most everything he mentioned in his post above. Permit me to add the following: There appears from what I observed, to be two main types of focus adjusted 35mm f1.4 ASPH lenses.

 

Type 1) Those that appear to be optimimized for correct focus at f1.4 in main area of depth of field where upon stopping down, rearward focus shift occurs, causing subject to go somewhat out of depth of field quite quickly until approx f5.6-f8, where the significantly large depth of field at f5.6-f8, covers any focus shift or anomoly.

 

Type 2) These lenses appear to be adjusted so that they front focus moderate to slight at

f1.4, putting the subject at the very rear edge (rear) of the depth of field or just beyond it. Subject is rendered somewhat soft, especially if viewed at 100% or prints large. Upon stopping down, focus shift causes the depth of field to move backwards and the subject is then squarely placed in depth of field beginning at f2 and especially anything beyond f2. It stays within depth of field upon stopping down even to f8 etc. It seems for whatever reason, lenses that have never been adjusted from original factory setting show that many silver 35mm f1.4 lenses came adjusted as what I describe as type 2, whereas I've found many black ones regardless of vintage are more or less type 1.Iits not an absolute nor something that one can rely on, especially that lenses throughout their life may have been worked on or focus calibrated. I'm not convienced as Lars mentioned that there are differences between silver and black lenses...but it appears that way.

 

Of course minute differences in the focusing biases of M8/M8.2 and M9 bodies to front or rear focus with lenses will have a profound affect just how ones 35mm f1.4 ASPH focuses on a particular body. Some lenses slightly front focus, others backfocus....so often a compromise has to be made in regard to how a body is set up...unless all lenses and a body are simultaniously matched...and even then a lens like the 35mm f1.4 ASPH and a few others may have slight front or back focus due to their inherent designs, when all other adjusted lenses seem fine.

 

I suspect the Zeiss ZM Sonnar 50mm 4 is exactly the same story. Those optomized for f1.4 will back focus upon stopping down whereas those that originally came optomized for

f2.8, will be out of the depth of field at f1.4 and somewhat at f2.0 until the focus shift catches up by f2.8....all somewhat analogous to what I described above, for the Leica 35mm f1.4 ASPH.

 

Dave (D&A)

[rolu]

... or by giving the focus ring a little bump in the appropriate direction when you are stopped down.

 

Just, how much is a little?

 

OK, if I shoot a portrait at a distance of 1m or 1,5m, I can focus on the nose, eyebrows - whatever front-focus compensates for the shift. (requires some testing for each lens)

If I shoot sth else, especially more remote, how much in front should I focus?

 

Is the shift proportionate to the log scale of the distance ring?

Can the shift be adjusted for by the same amount of turn of the ring?

- If so, one could get along with (a lot of) practice and best restricting oneself to one aperture setting in the problematic zone (f/2 - f/4 for type 1 in Dave's above post).

[carstenw]

You have to learn it for your copy, and people do do this. Experimentation and muscle memory. It doesn't help the resale price though.

[Guest mc_k]

...requires some testing for each lens...

You need to test the lens at the distances and apertures you will use it.

...Is the shift proportionate to the log scale of the distance ring?

This is more art than science--I am just suggesting you have a general idea of where your lens is off and a general idea of how much difference a minimal nudge to the ring makes. Like for example I have a lens I know is off about 5 in. at 10 ft., and I know the smallest correction I can make to the ring will just about cancel that 5 in. I think nudging the focus ring is a pretty common practice. Of course most will not need to bother, it all depends on how exacting your application is.

 

(BTW I think the error profile for a lens depends on the individual cam and shim--there is no general relationship throughout the range.)

[pklein]

As others said, a well-adjusted 35/1.4 Lux Asph is spot-on at f/1.4, back focuses slightly at f/2-f/4 or 5.6, and is OK at f/8 and narrower. This can usually be compensated for by focusing on the front of the zone you want in focus, in other words, on the very closest thing you want in focus. If you're really picky, you just learn that for f/2-5.6, focus on the tip of someone's nose rather than their eyes. Or on the ground a bit in front of them. Or use the "nudge" technique as mentioned above.

 

In a pinch, just take the picture, it's usually OK. This is how a friend of mine deals with focus shift--he ignores it. :-)

 

Another technique is to have two lenses: The 35 Lux you use only wide open and at f/8, and a Summicron or Voigtlander 35/2.5 that you use for all other stops.

 

The Voigtlander 35/1.2 is not quite as scary sharp as the Lux, but it doesn't focus shift for practical purposes.

[rolu]

... In a pinch,

just take the picture, it's usually OK. This is how a friend of mine deals with focus shift--he ignores it. :-)

...

 

(;-))

 

Great! - You put it in a nutshell !

[Guest mc_k]

makes you wonder how many M8s were returned for "focus shift"

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Hallo,

Look here: Leica M

[Alnitak]

The entire subject of the focus shift of the 35 'lux ASPH has been beaten to death at least twice in this forum. The shift exists; it may be more or less noticeable with different specimens because of minute differences in the factory focus adjustment, or because the owner is a more or less fanatical pixel peeper, but definitely NOT because of exterior finish. It is true that a digital sensor can show up minimal shifts of focus in a clearer way than film can, however. This, expressed in the most direct and brutal way, is because a silicon sensor is sharper than a piece of film.

 

This said, my own specimen which seems to be about average, gives me no problem at all with real-life three-dimensional subjects at normal shooting distances. The pictures come out just fine. To quote the immortal Alfred E. Neuman: "Who, me worry?"

 

The old man from the Age of Film

 

As a youthful consumer of Mad Magazine, I believe the correct quote would be "What, me worry?" which is exactly my approach to the focus shift "problem."