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75/1.4 Summilux calibration


johnkuo
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I bought it used and turned out the focusing mount was damaged. I had it repaired at Solms, supposedly also adjusted as part of the repair.

 

I understand that the lens exhibits focus shift. On my M8, all my other lenses seem to focus correctly. The 75 summilux appears to be calibrated at f/3.4. Wide open it has a slight front focus. As I close down, the focus shifts to the back. By f/3.4 it's dead on. The rest of the apertures are covered by DOF.

 

I have emailed Don at DAG, and his response is that he can adjust it to be perfect at f/1.4, but by f/4 I will notice back focus. He also asked what is the most common distance I shoot at. I'm mostly interested in using this lens wide open at mid distance.

 

I wonder if anyone had similar experience, and what aperture/distance was optimized. Your feedback is appreciated.

 

Thanks.

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I have emailed Don at DAG, and his response is that he can adjust it to be perfect at f/1.4, but by f/4 I will notice back focus. He also asked what is the most common distance I shoot at. I'm mostly interested in using this lens wide open at mid distance.

 

I find it hard enough to nail this lens wide open that testing for this problem is a bit like looking for a needle in a haystack. FWIW, my 1st Gen. 75 Lux doesn't appear to have any focus shift, but I missed a couple of shots a bit, so maybe it is just selective.

 

I think it ought to be possible to teach yourself to focus correctly with *your* lens. For example, one typically gets different results when focusing from closer and focusing from farther than the point in focus. One also gets different results when focusing back and forth, and when just focusing directly to the sharpest point and no further. One of these methods ought to suit the lens wide open, to give you more keepers. For my lens, it seems to work best when I focus from infinity and down, and stop when it is sharp, rather than going back and forth.

 

DAG has a great reputation, and can adjust stuff, but I have never heard that he can fix focus shift. I suppose that might require more expensive equipment, since he would have to realign all the elements.

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he can adjust it to be perfect at f/1.4, but by f/4 I will notice back focus.

 

I think this is true with many lenses. One thing I've noticed with the M8 is that you have to compromise. On one hand you have back focus. On the other you have diffraction and spots(from a dirty sensor) showing up already around f5.6.

 

My conclusion is that I'd prefer my lenses to be spot on focus wide open in the close(< 2 meters) range.

I pretty much keep my lenses wide open to 1 stop from wide open. If I wanted full depth of field and had the light to shoot like that then I might as well use another make of camera.

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...

 

DAG has a great reputation, and can adjust stuff, but I have never heard that he can fix focus shift. I suppose that might require more expensive equipment, since he would have to realign all the elements.

 

Carsten,

 

Thanks for your reply.

 

I didn't expect DAG to fix focus shift. My understanding is that it's an inherent property of that particular optical design and cannot be eliminated. I'm just trying to decide whether to place the calibration point so that the effect of focus shift is minimized by making the most apertures usable (which I think Solms did by optimizing for f/3.4), or just to make sure f/1.4 is spot on at the expense of more back focus at all other apertures.

 

Your suggestion on various focusing technique is helpful, and I do have some idea of the amount of adjustment I need to correct for the slight front focus at f/1.4. I think my dilemma comes from the fact that I do like to use this lens wide open, hence my consideration of optimizing it for f/1.4.

Edited by johnkuo
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I cannot see much focus shift on this lens. Mine was perfect, until it started to show mild backfocus at all apertures.I think the rangefinder was drifting off slightly. I sent the lens to Will van Manen, who found out that it was within spec, but at the limit of the tolerance. He adjusted it to be in the middle of the tolerance span. My main body is in Solms at the moment and will return soon, fully adjusted, and I expect the lens to focus correctly at all distances and apertures again.

In theory a lens that exhibits focus shift should be exact or minimally frontfocussing wide open and the shift will be compensated by DOF on medium and small apertures. A slight correction (just move your head a bit), on wide,but not fully open apertures may be needed.

The combo Summilux 75/M8 is merciless for focussing. But extremely worthwhile.

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My understanding is that it's an inherent property of that particular optical design and cannot be eliminated.

 

There is more to it than that. I am pretty sure that even if my 75 Lux has a touch of focus shift, it isn't nearly as bad as what you describe. My 35 Lux ASPH also doesn't have focus shift. I re-tested it when it returned from Leica (the front was getting loose), very carefully on a tripod, and it still doesn't. This lens is infamous for the focus shift "inherent" to its design. I think it is probably more accurate to say that Leica cannot get tolerances tight enough to guarantee that there will be no focus shift, and so there are some with, and some without.

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There is more to it than that. I am pretty sure that even if my 75 Lux has a touch of focus shift, it isn't nearly as bad as what you describe. My 35 Lux ASPH also doesn't have focus shift. I re-tested it when it returned from Leica (the front was getting loose), very carefully on a tripod, and it still doesn't. This lens is infamous for the focus shift "inherent" to its design. I think it is probably more accurate to say that Leica cannot get tolerances tight enough to guarantee that there will be no focus shift, and so there are some with, and some without.

 

Thanks for the explanation and everyone's comments. I don't notice much focus shift on my 35 lux asph either. I rarely shoot more than 3 stops from wide open. At the moment I'm leaning towards having DAG calibrate it for wide open performance.

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I bought it used and turned out the focusing mount was damaged. I had it repaired at Solms, supposedly also adjusted as part of the repair.

 

I understand that the lens exhibits focus shift. On my M8, all my other lenses seem to focus correctly. The 75 summilux appears to be calibrated at f/3.4. Wide open it has a slight front focus. As I close down, the focus shifts to the back. By f/3.4 it's dead on. The rest of the apertures are covered by DOF.

 

I have emailed Don at DAG, and his response is that he can adjust it to be perfect at f/1.4, but by f/4 I will notice back focus. He also asked what is the most common distance I shoot at. I'm mostly interested in using this lens wide open at mid distance.

 

I wonder if anyone had similar experience, and what aperture/distance was optimized. Your feedback is appreciated.

 

Thanks.

 

John

 

This took a long time for me to get right. The short answer is that you would normally want this optimized for f1.4 and at your normal working distance (generally 2-3meters). This allows the lens to display its unique fingerprint .

 

After that you have to know the lens and make manual adjustments to obtain optimum focus. For example I know how my lenses perform in three zones (close ...2-3M, intermediate ...7-10M and at infinity. ) and how much focus shift to expect.

 

Leica has picked a decent compromise. If you were doing normal travel photography...having slight front focus wide open works. If you are shooting a lot of portraits ....it will not be as good..you will misfocus more often.

 

I would also tell you from experience with 6 M bodies plus numerous borrowed M8 s that ...rangefinder calibration is very difficult to optimize. The body may have very slight backfocus and your other lenses are possibly slightly front ...this doesn t mean they are out just that within the acceptable range they tend toward back or front. I don t think you can test your m8 with any lens shorter than a 50mm. Leica uses a silver/brass mount 90/2 summicron as one of the tests .

 

Roger

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John

 

This took a long time for me to get right. The short answer is that you would normally want this optimized for f1.4 and at your normal working distance (generally 2-3meters). This allows the lens to display its unique fingerprint .

 

After that you have to know the lens and make manual adjustments to obtain optimum focus. For example I know how my lenses perform in three zones (close ...2-3M, intermediate ...7-10M and at infinity. ) and how much focus shift to expect.

 

Leica has picked a decent compromise. If you were doing normal travel photography...having slight front focus wide open works. If you are shooting a lot of portraits ....it will not be as good..you will misfocus more often.

 

I would also tell you from experience with 6 M bodies plus numerous borrowed M8 s that ...rangefinder calibration is very difficult to optimize. The body may have very slight backfocus and your other lenses are possibly slightly front ...this doesn t mean they are out just that within the acceptable range they tend toward back or front. I don t think you can test your m8 with any lens shorter than a 50mm. Leica uses a silver/brass mount 90/2 summicron as one of the tests .

 

Roger

 

Roger,

 

I agree that it should be calibrated for f/1.4 for the normal distance I shoot. My usage is low light portrait type of work. For mid aperture travel photos, I would use other lenses.

 

Thanks for sharing your experience.

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After sending my 75lux for cleaning (not to Leica) around 5-6 years ago, the lens returned totally off focus. I sent it to Leica and it returned still off. Until recently, I never attempted to calibrate it again. Recently, I sent my M8 for upgrade so I sent the 75 with other lenses for focus calibration. Now it is perfect. workable from 1.4 and above, no noticeable focus shift. My lesson is- if you need to calibrate focus, they don't always get it right at the first time. it worth sending it over again to get your lens to working condition. I have ta similar situation with my 35 lux apsh now. my 35lux is a victim for extreme focus shift. I sent it too, with the M8 to Solms, but It returned in the same condition. I sent it again and I hope this time the lens will work as other's 35lux apsh does, that is- that the focus shift will be compensated by DOF increase.

 

Here are some samples to 75lux after the calibration. Some @ 1.4, the last, 100% at closer aperture- to prove no focus shift:

 

L9991355.jpg photo - ramig photos at pbase.com

 

Leica 75 summilux @ f/1.4 photo - ramig photos at pbase.com

 

Leica 75 Summilux @ f/1.4 III photo - ramig photos at pbase.com

 

Leica 75 Summilux @ f/1.4 II photo - ramig photos at pbase.com

 

100% crop:

 

75 lux 100% crop photo - ramig photos at pbase.com

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Roger,

 

I agree that it should be calibrated for f/1.4 for the normal distance I shoot. My usage is low light portrait type of work. For mid aperture travel photos, I would use other lenses.

 

Thanks for sharing your experience.

 

I also did not see much focus shift with the 75 as its stopped down. I believe their is a little with each of the summiluxes(35/50/75) . You may see some focus shift (a different cause) as you change distance ....this shows up in the 135APO . My intentions are similar...its a special purpose lens best for low light portraits . Lower in contrast(at 1.4) but with excellent smooth bokeh.

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