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35mm Summilux FLE focus shift and rangefinder inaccuracy


PCPix

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2 hours ago, Kim Dahl said:

Thanks for the exciting discussion.  As I understand it, several Leica M lenses suffer from focus shift.  Can one tell how to do an easy test to see if one's lenses of focus shift?
tanks ☺️

Yes do not follow reviewers' advices :D. Unless you spend your life shooting macros or closeups there is little point in doing tests below 2 meters in my experience. So put your camera on a tripod at 5m subject distance for example, focus carefully at f/1.4, do not touch your focus ring after that, then shoot successively at f/1.4, f/2, f/2.8 etc. By doing side by side comparos you will see (or not) that your pics are sharp for instance at f/1.4, remain more or less so at f/2, then become softer at f/2.8 and so on. Another way is focusing at f/2.8 if your lens is calibrated at f/2.8 like my Summilux 35/1.4 v2 or possibly a ZM 50/1.5 if your copy is calibrated this way. Then shoot successively at f/2.8, f/1.4(1.5), f/2, f/4 etc. 

Edited by lct
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The pictures show the distance scale setting when focussing on something 'far away'  by means of the Visoflex EVF. One focussed at f/1.4, the other focussed at f/4.0. (B.t.w. in my case focussing with RF is spot-on at f/1.4). In normal use, this focus shift never bothered me. YMMV.

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To test RF /lens calibration you need to test at 3 distances .     

                     2 meters ...make a lazy 8 focus chart and stand 6 feet away .  You will see everything you need to know .  I use a white board and make target 36inch wide with marker .  

                    6 meters ..this is the prime focusing distance that Leica measures .   

                    infinity ..if infinity is off you will never get the body calibrated correctly . 

 

What is important to consider is that both the M body and the M lens have tolerances .  Just because they are new or Leica says they are in SPEC doesn t mean they will work well together .  Lets say you have body that is slightly back focusing and good with most your lenses .  You use a lens that back focuses slightly and the system is now compromised .   

So you send you camera and lens to Leica .   What do you think they do .   They check the camera and hopefully can get it back in the middle of the tolerances .  This was not possible with the the M8 but after they repositioning the sensor on the M8.2 ..it is .   

Then they adjust the lens to be in spec .  The Summilux and Noctilux lenses cause them fits .  They are often at the edge of acceptable calibration .   We tested 12 50/1.4 asph (brand new) summiluxes to find ONE that was not at the edge of the tolerances .    

But what happens if they adjust the camera to slightly front focus to offset the lens .  DAG used to recommend dedicating a 50/1 Noctilux to a specific body and calibrating the two together . Not so good for your other lenses . 

A lot has improved since the M8 ..Leica revamped their calibration process . My cameras always come to me well calibrated .   New lenses have very little focus shift but the older designs  especially the Sumiluxes and Noctiluxes (designed for film ). can still be a legacy challenge .   

If you bump you camera you can knock the RF out of calibration ....this has never happened to me. 

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Just checked it again with my 35 FLE. Perfect focus at f/1.4 (DOF from about 1/3 before focus point to about 2/3 beyond). It is known that the focus shifts slightly with aperture, however it is very difficult to see without using a tripod and a 45° ruler.... In typical sharpness tests without correcting focus shift, sharpness at the focused point is still roughly at the same level at 1.4 and 2.8. At the real focus it is slightly sharper at 2.8, of course. Thus, at least for me, focus shift of the 35 FLE is not relevant.

That said, my 35 FLE was at the Leica service shortly after I bought it. Since that service (four years ago) sharpness has been really perfect (for me)! 

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17 hours ago, FrankX said:

Just checked it again with my 35 FLE. Perfect focus at f/1.4 (DOF from about 1/3 before focus point to about 2/3 beyond). It is known that the focus shifts slightly with aperture, however it is very difficult to see without using a tripod and a 45° ruler.... In typical sharpness tests without correcting focus shift, sharpness at the focused point is still roughly at the same level at 1.4 and 2.8. At the real focus it is slightly sharper at 2.8, of course. Thus, at least for me, focus shift of the 35 FLE is not relevant.

That said, my 35 FLE was at the Leica service shortly after I bought it. Since that service (four years ago) sharpness has been really perfect (for me)! 

This is ecouraging to hear Frank... Up close at 1.4 mine has the focus right at the front of the area of acceptable focus - not the 1/3 - 2/3 as you describe, which technically is as it should be... I'm currently awaiting an email response from the technicians at Wetzlar (via Mayfair).

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  • 3 months later...

Here's an update: The lens went back to Wetzlar (via Mayfair/London).

Recalibration and service completed at no charge (bought new in 2017 by myself, 2016 manufacture date).

The close up focussing is better, with the target sitting about midway through the DOF at f/1.4 and 1metre - focussed with rangefinder, on tripod.

At f/2 all is good, at f2.8 - 4 the lens does focus shift backwards as previously, however the target does stay 'just' inside the front of DOF (which it did not before) and well within the margin of error expected when handholding (we are talking millimetres here).

From f/5.6 onwards all is fine.

All apertures and rangefinder accurate on infinity hard stop.

Overall, a very fine/subtle adjustment which has corrected my original complaint. Added to the complimentary recalibration, I can say I am happy with the lens and the service recieved from both Mayfair and Wetzlar.

100% crop handheld at MFD with rangefinder and f/1.4 (sorry - no cats available;-)

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2 hours ago, PCPix said:

100% crop handheld at MFD with rangefinder and f/1.4 (sorry - no cats available;-)

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Good demo of calibration, but on a different topic, I much prefer having eyes and nose in focus. Mike Johnston likens it to looking at a typo.

https://theonlinephotographer.typepad.com/the_online_photographer/2019/11/what-is-bokeh-and-the-dogs-nose.html
 

Jeff

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14 minutes ago, lct said:

At 0.7m subject distance, total DoF is 20 centimeters on a 35/1.4 lens at full aperture. Better shoot a cat than a dog to get both eyes and nose in focus then :D.

Or use a different lens, or stand in a different place, or stop down, etc.  The viewer doesn’t care about gear or technique.  As I wrote, a separate topic.

Jeff

Edited by Jeff S
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As Mike Johnston wrote in the linked article… “I see a lot of close-up portraits of dogs where the eyes are in focus and the end of the nose isn't, which bugs me like a bad tpyo”. 

I agree, but that’s what makes photography interesting…we define and present our subjects in different ways. Some even care about the subject as much as the bokeh.

Jeff

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I have nothing against Mr Johnston but this is a thread about a 35/1.4 lens so it doesn't come (to me) as a surprise if the eyes and the nose of a dog are not sharp when shot at 0.7 metre with such a lens at full aperture.. It's just what i wanted to say :cool:

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4 hours ago, Jeff S said:

Mike Johnston likens it to looking at a typo.

An interesting read - thanks for the link... he also famously uttered the immortal words “King of Bokeh” about the 35mm Summicron - which even he says “it’s not”! It always seemed odd to me that such a title was for a wide lens and not a short tele...;-)

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9 minutes ago, PCPix said:

he also famously uttered the immortal words “King of Bokeh” about the 35mm Summicron - which even he says “it’s not”! It always seemed odd to me that such a title was for a wide lens and not a short tele...;-)

I’m aware, and if you read the whole link, he once again explains the ordeal, which he now calls embarrassing. 
 

Jeff

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