Focus how good is good enough?

[Manicouagan1]

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Both my M240 and M246 have gotten a lot of use and traveled a lot.  I ran a simple test on my 50mm f1.4 ASPH, 75mm f2 APO and 90mm f2 APO.  

 

I checked both cameras using my Lens Allign tool (obviously in manual focus mode) at a distance of 3 meters.  All images show the optimum focus wide open anywhere from 5 to 10 cm behind the point I focused on.  

 

Most of my images are taken at or near infinity focus and typically at f4-f8 so the back focus is rarely noticable.   Nonetheless I am a bit of perfectionist.  Other forum discussions indicate the obvious that there is some level of unavoidable offset between the point of optimum focus on and image and visibly perfect allignment of the rangefinder patch.  In other experience is 5-10cm backfocus at 3 m significanly beyound what others find the system will achieve?  

[Frase]

Thats not good enough I would say, on testing my lenses (M9) I would be upset if they were 2-3cm out. 

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[Jeff S]

Both my M240 and M246 have gotten a lot of use and traveled a lot.  I ran a simple test on my 50mm f1.4 ASPH, 75mm f2 APO and 90mm f2 APO.  

 

I checked both cameras using my Lens Allign tool (obviously in manual focus mode) at a distance of 3 meters.  All images show the optimum focus wide open anywhere from 5 to 10 cm behind the point I focused on.  

 

Most of my images are taken at or near infinity focus and typically at f4-f8 so the back focus is rarely noticable.   Nonetheless I am a bit of perfectionist.  Other forum discussions indicate the obvious that there is some level of unavoidable offset between the point of optimum focus on and image and visibly perfect allignment of the rangefinder patch.  In other experience is 5-10cm backfocus at 3 m significanly beyound what others find the system will achieve?  

 

Have you eliminated lens focus shift (focus change as a result of stopping down) as a potential variable?  

 

I assume you conducted careful tripod tests, comparing LV with the RF/VF.  I found virtually identical results when I conducted such tests with my M240 (albeit without LensAlign).

 

Jeff

[sblutter]

For shots that require a tack sharp focus point I go with LV - one of many reasons I love my 240.  Sure I've had it a long time with other cameras - but I'm a 40yr+ M guy

[pico]

When you find that a few of your photographs are endearing, highly successful, and the focus is out by a few cm, worry not. Many of mine are that way and nobody has complained, and I've had hundreds published.

 

Focus upon the image, not upon the focus.

.

Edited February 17, 2017 by pico

[lct]

5-10cm back focus at 3 m can hardly be considered normal per se. Wouldn't work for me as i shoot often at 2m/3m focus distance but if you like the results you get near infinity i see no reason to bother unless you happen to shoot at closer distance from time to time. 

[Fgcm]

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Have a look at this tread.

 

http://www.l-camera-forum.com/topic/118043-m9-coincidence-at-infinity/

 

Focus problems can be fixed in minutes with simple tools.

Ciao

Franco

[edwardkaraa]

I personally would only tolerate around 1cm at minimum focus distance and around 3cm at 3m would be the borderline acceptable results. All but one of my lenses are spot on, and only one lens backfocuses by exactly 1cm at mfd. 5-10cm would be time for a visit to the local Leica repair shop.

[Vec]

My M240 was around the same level of off. With most of my lenses, it was ok. With the 90 Summicron, it was a nightmare and I would only accidentally get shots unless I used live view (which I really don't like much).

 

Like Fgcm noted above, it's an easy process. All I did was tweak the infinity setting a tiny bit and it was 95% better. It took 10 minutes and a good few stiff drinks afterward (not before) to calm my nerves. 

 

At the end of it at minimum focus I was around 2cm behind at minimum focus and dead on past maybe 2m. I could have started to tweak the arm length, but I didn't feel like making a tool for that adjustment since it wasn't off enough to bug me enough.

 

-George

[lct]

[...] All I did was tweak the infinity setting a tiny bit and it was 95% better. It took 10 minutes and a good few stiff drinks afterward (not before) to calm my nerves. [...]

 

Did this in the past but the trick can be great for one lens and a pain for other ones so i prefer having each lens fixed as it should be. YMMV. No need to send the lens in to Wetzlar for that but the chosen workshop must have a solid experience with FLE lenses like 50/1.4 asph & 70/2 apo.  

[david strachan]

Yes, you can't just tweak your camera to suit every lens.  They are all a bit different, and need to be serviced themselves, to fit the normal corrected, standard calibrated, camera.

Not the other way round.

 

..

Edited February 21, 2017 by david strachan

[otto.f]

When you find that a few of your photographs are endearing, highly successful, and the focus is out by a few cm, worry not. Many of mine are that way and nobody has complained, and I've had hundreds published.

 

Focus upon the image, not upon the focus.

.

I agree with the image being more important than the focus. So I would publish a photo of the focus was off but it didn't harm the image quality in the broader sense. But I would not call myself a perfectionist as OP states if I would send it in for readjustment. 5-10cm on 3m is just plain wrong.

I once stepped over from an SLR system to the Leica M system because the lenses are on the whole just a bit better. So I would not compromise on that last (repairable) surplusvalue of the M system, otherwise I could have stayed with SLR.

Edited February 21, 2017 by otto.f

[Vec]

I did cross-checks with my two most critical lenses, the 90 f/2 Cron and the 50 f/1.4 Lux and they seem to be matched up well enough. Everything else I have is wider and anything that's off fits within DOF. The 50mm was back focusing around 0.5cm compared to the 90mm 2cm at minimum focus so that got me happy enough to not send in the whole kit to get serviced.

[Rangefinder]

Interesting thread!  I'm a new Leica user and noticed the 90mm Cron lens I purchased used was a bit difficult to focus properly.  I took it to my Leica dealer and he sent it to New Jersey.  Low and behold, it wasn't all my issue.  They made whatever adjustments necessary and I should have it by the end of this week.

 

Mike

[bocaburger]

All my lenses are spot on with both my M240 bodies.  I checked close-focus on a bar code, mid-range on a car license plate, and infinity on the Goodyear blimp as it made its daily pass

[sblutter]

Interesting thread!  I'm a new Leica user and noticed the 90mm Cron lens I purchased used was a bit difficult to focus properly.  I took it to my Leica dealer and he sent it to New Jersey.  Low and behold, it wasn't all my issue.  They made whatever adjustments necessary and I should have it by the end of this week.

 

Mike

Assuming its the f:2.0 version - that lens is very tough to focus wide open.  Good luck! 

[Rangefinder]

Yes, sir, sblutter, it is the f2.0 ASPH.  Sorry, I should have mentioned that.  I'm looking forward to getting it back.

 

Mike

[FeralCoton]

My mp240 was fine, but I noticed the 24mm elmarit didn't quite focus at infinity (it seemed like it needed about 1/16 inch past the stop to line up the rangefinder. I had to send the camera and lens to nj. I was fortunate to get a good turn around, but they adjusted too far in the other direction so now my 50 lux and 35 cron focus infinity at a bit before the infinity stop. Wonder if adjusting the hex screw adjus will fix it?

 

 

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Edited February 23, 2017 by FeralCoton

[Vec]

If you have lenses that don't agree on infinity then you don't have a simple camera calibration issue.

 

Basically, you have two different optical systems that need to be in sync, the lens/rangefinder system and the lens/sensor system. If your lens, when focused at infinity (ignoring the rangefinder!) takes a sharp picture at infinity (like a distant building or something) then the lens/sensor is fine. From there you calibrate the rangefinder to coincide with the lens/sensor.

 

But your problem is different it seems. Assuming your 35 and 50 agree on focusing but your 24 doesn't then the solution isn't to adjust the camera but the lens. Leica has ways of adjusting the lens to make it work right. Sometimes it's shimming the lens mount, sometimes it's other magic that I'm not really sure of.

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[FeralCoton]

That was what I hoped I sent them in. Then all front focused. I used a hex wrench and nudged the screw a very tiny bit as described in the above post. Now the lenses seem to agree. I'll explore tomorrow and hope all else is in focus.

 

 

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