Lux 50 ASPH soft/back focus issue

[Catatac]

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On the weekend, I noticed that my Lux was producing either back focus or soft focus issues. It is not stable when wide open. At times, it appears to be a back focus issue and at other times it appears to be a soft focus issue. I've had the Lux for several months now and was only on the weekend that I noticed this. Is it the lense or the camera (I tried with my other lense which is a Zeiss and it worked fine) ? Cleaned the coded area but to no effect. Lense and stops are locked properly in place.

 

Any help is really really appreciated !!!!

[Paul0303]

Just going through the same thing myself. First I thought it was the M8 but comparing with other lenses eliminated this. I'm planning to check the lens on another M8 in the next few days and if it is wrong then it's back to Germany with it (still under guarantee).

[carstenw]

Catatac, if you only have one lens, then try this: from a high vantage point, find a thin church spire far away on the horizon, set the lens to infinity, and make a photo. If it is in focus, check the near focusing limit very carefully. If both are in focus, there is no problem. If one or both are not sharp (keep in mind the haze at long distances; having a second camera to compare with would be good), then something needs adjustment.

 

If only one or the other of near and far is out of adjustment, then the near-far balance needs tuning, which requires removing the red Leica dot. You may want to just send the camera and lens in for focusing tuning. If both are out, then you may be able to fix it by turning the little rangefinder wheel small amounts with a 2mm Allen key. There are several threads here about how to do this. Here is one:

 

http://www.l-camera-forum.com/leica-forum/leica-m8-forum/27232-how-precisely-tune-your-rangefinder-15-a.html

[Eoin]

Catatac, it seems strange that you have not noticed the softness / back focus before now. I would suggest you check what has changed since you last used the lens with perfect results. For instance have you perhaps started to use a magnifier or a diopter lens on your camera, have you perhaps changed your glasses. If nothing has changed you need to check your focus against near and far objects and with as many lenses as you have to get an accurate picture of what's going on exactly.

[tom0511]

Shoot something "deep", like a field of grass, or a pieceof wood - you can easily see if it is just front or back focus.

Mine did backfocus and went in to Leica second time now because of that.

[Catatac]

To be honest I dont use the Lux that often but in the past the images have been razor sharp. I noticed it since the last weekend when a lot of images went soft. Nothing has changed in the past few months aside from using an IR cut filter (B+W) and I damaged a non-Leica lense (Zeiss). To give you an example is the following portrait. I focused on the person's nose but it is soft while his nose and shirt is sharp:

 

[wizard]

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Just a thought: Depth of field is quite shallow with the 1.4/35 fully opened up. If you photograph a person, as in the example above, you can never be quite sure that no movement occured between focusing and actually pressing the shutter release. Either the guy or you or even both of you may have moved an inch or two, ruining your intended point of focus.

 

Try to put the camera on a tripod and take some shots of non-moving objects to find out if there is a technical fault or if it is human error.

 

Andy

[Catatac]

Unfortunately the above is only an example. I did a few test shots of still objects and had the same problem.

[Paul0303]

Following on from my earlier reply I had my 'Lux Asph 50 checked at my local camera store and it definitely was a lens problem. The lens will be off to Germany next week and will likely be spending Christmas in Solms...

[ho_co]

Check it wide open. All Leica lenses should be in focus at full aperture, according to both E Puts and the LFI August 07 article mentioned below.

 

As one stops down a bit from full aperture with Leica high-speed lenses, one begins masking the edge rays and focus will shift slightly away from the camera. HOWEVER, the focus shift SHOULD remain within the depth of field of the lens and be unnoticed at normal magnification. That is particularly true with the 50/1.4 ASPH, whose floating element should minimize the effect.

 

With the change of having a two-dimensional sensor as compared to three-dimensional film, the M8 is a perfect instrument for discovering these traits. See in this regard the article 'Sense and Sensuality' in LFI 6/2007, pp 42-53.

 

My guess--based simply on others' experiences reported here--is that it's the lens; but obviously I can't know that any more than someone can know it's the camera. It could be either.

 

The problems are several: One uses a fast lens in low light, where depth of field is very shallow. It's often harder to focus accurately in low light as well. So if you or the subject moves by a quarter inch, you may be beyond the limits of depth of field. If you then examine the image at 100% on a monitor, you'll see discrepancies that we never saw with film.

 

You don't use the lens often, but if you go back and check what you've done with it before, you may find that it has been acting up all along.

 

As example: I've had a 75 Summilux for thirty years or so and been more than satisfied with it. But a couple months ago I used it extensively with the M8 and realized that it back-focuses. I hadn't noticed it before, but I didn't use it that often in the past; and now I used it with the M8's very precise focusing requirements. I think it's a problem that has been there all along, though of course I can't be sure of that.

 

(And as expected, your example picture shows minimal focus problem compared to my much earlier Summilux design.)

 

Good luck. You're getting a lot of advice here, and some of it may be good!

 

--HC

[Guest Bernd Banken]

After focussing with the patch in the middle of the VF you had to move the camera for this off center composition. Due to this movement 1. some small shift in distance could have happend or 2. the field of sharpness? of the lens doesn't match ( it's plane or bended?).

 

So better to test with no recompositon.

 

Regards

Bernd

[Catatac]

Thanks everyone for their advice ! It looks like I will need to do some further testing to check. My prior tests were with the aperture wide open and focus was soft but I need to do some proper fixed distance and stable tests. Given my superb eye-hand coordination skills (not), I dare not play with the rangefinder wheel though that sounds like great advice. If it is a lense issue (and its all pointing that way), then sadly, its off to Solms for my Lux.

[lars_bergquist]

A note on 'infinity tests'. You cannot do a valid infinity test on objects on the horizon, due to the atmosphere - haze and mirage. Your unaided-eye judgment of 'sharp' is not worth much. You must do it at optical infinity. This is when rays from a point object are in practice parallel. Now what does 'in practice' mean? A generally accepted rule is "object distance equal to or larger than 1000 x the focal length". In a 50 mm lens, this makes 50 m (164 feet). If you want to have a margin of safety, test at 100 m, but only on a still and crystal clear day! There is more shit in the air than you are aware of. Needless to say, you need a sturdy tripod and you must use either a cable release or the self-timer.

[Paul_S]

Thanks everyone for their advice ! It looks like I will need to do some further testing to check.

 

I just did similar testing with my Noctilux last week after being in Solms for adjustment (with camera). I made pictures at 1, 2, 3.5 and 5 meters and some 'almost infinity' shots. Aperture range for each picture up to f/5.6.

Good news for me was proper focussing at f/1-1.4 at all distances, and visible focus shift up to f/5.6, beyond DOF at all distances too (amount is approx. 10%, i.e. at 1m focus shifts 10 cm at f/5.6). Good luck with your testing!