"Calibration worthy" L39 to Sony E adapter?

[Daimon]

Has anyone tried to calibrate L39/LTM lenses using adapters on Sony-E full frame camera?

i.e. having adapter with precise registration distance so I could adjust shims in lenses based on photos done on Sony camera.

I already have Nikon focusing screen + magnifying glass to check TTL focus on actual L39 camera but that's very tedious process, especially on bottom loaders.

I've seen some people mentioning dedicated Leica TTL viewers but cannot find anything now.

I'm aware that perfect solution would be digital "M" Leica camera but that's out of my budget.

 

[peterm1]

Do you really need any calibration? Certainly you do if using the lens on a Leica rangefinder camera as the lens calibration must correspond to that of the rangefinder in the camera. But on a mirrorless camera like a Sony E mount your focus is not determined by the lens' calibration, it is determined optically through the EVF (using focus peaking or otherwise). Mostly if the calibration is a bit off and the lens cannot quite reach infinity then stopping down corrects this as the DOF at infinity can fix the short focus. If it is way off though some recalibration may be needed - in this case the thickness of its shims may need to be reduced. If it is off in the other direction and it more than reaches infinity, it's not really an issue when shooting on a mirrorless, however as focus at all focus distances are available in any event.

I have had one LTM lens (a Canon 50mm f1.2) professionally recalibrated but this was because it was well off calibration somehow and I wanted to use it on a Leica M8. This required the adjustment shim inside the lens (which was quite thick) to be lapped to be made more thin. This was done by trial and error quite simply enough - take the shim out, lap it on a diamond honing plate for a few minutes, put it back into the lens, test the focus to see if it now corresponds to the rangefinder by taking a picture then if it does not, lap some more until everything is kosher. As I say this was not so much an issue for the times I use the lens on a Sony E mount (which I sometimes did) but more for when I wanted to use it on a leica M.

 

[Bill Jones]

Has anyone tried to calibrate L39/LTM lenses using adapters on Sony-E full frame camera?

i.e. having adapter with precise registration distance so I could adjust shims in lenses based on photos done on Sony camera.

I already have Nikon focusing screen + magnifying glass to check TTL focus on actual L39 camera but that's very tedious process, especially on bottom loaders.

I've seen some people mentioning dedicated Leica TTL viewers but cannot find anything now.

I'm aware that perfect solution would be digital "M" Leica camera but that's out of my budget.

I completely agree with what Peterm says.
It's not clear to me what you are calibrating for. If it's to set the lens up tones on an L39 camera then you need to beware that many (most?) mirrorless adapters err on the short side (based on my experiences using or checking numerous adapters for e-mount over the past 12 years.)
Using a Sony E mount to calibrate them could leave you with your lenses set too long for L39 mounts. They then would not focus to infinity.

Bill

 

[Daimon]

Yes I need calibration because lenses are not setup properly - require re-shimming

And yes I'm aware that cheap adapters do not follow proper register distance and that's why I'm asking about experiences with proper ones

 

[Timmyjoe]

Are you trying to calibrate LTM lenses with your Sony-E full frame camera so the LTM lenses will be calibrated properly on your LTM cameras, or are you just trying to calibrate the LTM lenses so they work properly with your Sony-E full frame camera? If it's the latter, I've found most any lens will work with a mirrorless camera if the FFD of the adapter puts the lens in the ballpark of the proper distance from the sensor.

If it's the former, it's a little more complicated than that. It sounds like you want to use your Sony-E full frame camera as a sort of lens collimator. That could be done, but you would need an LTM adapter that is VERY PRECISE, I mean measured down to thousandths of a millimeter. And even then, your Sony-E full frame camera would also have to have a flange to sensor distance that is precise to thousandths of a millimeter. Not sure how feasible that is.

Best,
-Tim

 

[Daimon]

Thx Tim. Yes, that's the idea. Have adapter precise enough so Sony can be used to calibrate LTM lenses so they work "good enough" on LTM cameras. Right now some of them are completely off (FSU ones).

As mentioned I already have focusing screen so I can literally check TTL focus on LTM camera but it's very tedious process for initial shim adjustment. I might use it for final fine tuning

 

[Sonnar Brian]

FSU lenses are not calibrated to the Leica standard. An Adapter calibrated for Leica Lenses will not properly focus an FSU lens across the full range unless the lens has it's focal length adjusted and the main shim set for the Leica standard.

 

[Daimon]

That's the point - adjusting shim for shorter distance correctness on LTM cameras.

Actually some of FSU lenses I have now are not adjusted for FSU cameras either. One is so off that it reaches infinity at 10m mark

 

[Timmyjoe]

Also keep in mind that the LTM camera has to be calibrated as well. It's FFD has to be spot on, and it's rangefinder needs to be calibrated properly. An out of calibration rangefinder will not focus LTM lenses, even if the LTM lenses are properly collimated.

Best,
-Tim

 

[Daimon]

Checking FFD should be easier though? I.e. I can just verify it with depth micrometer across frame?

Lense focusing looks to be more difficult to check properly at home and that's why I'm trying to make process easier

 

[mapgraphs]

...

i.e. having adapter with precise registration distance so I could adjust shims in lenses based on photos done on Sony camera.

...

There's an assumption here that a Sony body will have an accurate registration distance that you can use with an accurate, within-spec adapter. I would say from my own efforts and some anecdotal views, all you will do with this approach is interject another variable. Sony in the past at least used shims to adjust the registration distance of the sensor array as opposed to a lock screw. So first you'd need to find out if the Sony is spot on, then the adapter. Practically every adapter I have is slightly off, including some ltm-M adapters. I treat the published registration distance, both for cameras and lenses as the ideal. The combined in and out of tolerance as the real. Shim the adapter, not the lens...

 

[Sonnar Brian]

That's the point - adjusting shim for shorter distance correctness on LTM cameras.

Actually some of FSU lenses I have now are not adjusted for FSU cameras either. One is so off that it reaches infinity at 10m mark

I've seen much worse. Usually FSU lenses require an extra 0.12mm shim to account for the 52.4mm vs 51.6mm standards.
You can set the main shim for precise focus at a specific distance and Aperture setting. Best to adjust focus for about 3m at F1.5, usually infinity will be good at F2.8. FSU lenses have a +/- 1% allowed deviation on focal length. SO- results are all over the place. Adjust 200 and more FSU lenses for a Leica, each is an individual challenge.

 

[Sonnar Brian]

What you need is one "Gold Standard" LTM lens that you trust the calibration. That should be a lens made to the Leica standard, or an FSU lens that you want to match all others against. Once that lens properly focuses from close-up to infinity at the preferred apertures, you can use the Mirrorless camera with the adapter to adjust other lenses to within a "Ballpark". The problem is difference in actual focal length of the lenses will affect exact agreement across the full focus range. You are best to perform final calibration on the camera the lens is to be used on.

I use a Canon III to test the distance scale of lenses, measuring against a known target set at 5m. Step 1 is to make sure the focus scale of the lens is good. If it fails, means repositioning the helical in the mount of the J-3 or building up the Cam of the lens. After that- set the actual focus of the lens using the main shim. If focus does not hold across range, I move the rear group of the lens to adjust focal length.

These days- I refer people to Skyllaney for adjusting lenses. I've spent a lot of time adjusting can-of-worms FSU lenses.

 

[JeffS7444]

I think you could DIY such an adapter by adjusting an off-the-shelf lens adapter such that a known-good lens focuses correctly. Ideally, you want to start with an adapter which allows focusing past infinity, because then it's simply a matter of adding shims to achieve the correct flange to focal plane distance.

 

[Daimon]

Thx Brian (as always) for great concrete tips.

Also to Jeff comment - yeah that's ideal cost wise but as Brian mentioned I need some "gold standard" lense. Thought that I could try to use precise adapter as gold standard but by looking at comments that may be hit or miss.

Maybe I'll try measure which of my LTM cameras has most up to spec FFD and then check which of the lenses works fine on that camera. That lense could later be my "gold" standard.

 

[Daimon]

Following experiment anyway.

Bought "precise" L39 to Sony E adapter - it has very tight fit in Sony and all M39 lenses screw in at exactly same 12 o'clock position as in normal L39/M39 cameras - that's a good sign.

How do I know if Sony + Adapter end up having exactly same registration distance?

I don't. But I checked several of my FSU lenses by using lens calibration target + ruler to set the camera (using registration plane mark) at exactly 1m + setting lense at exactly 1m mark + checking infinity later.

Results:
- 1951 Industar-22 - spot on both 1m and Infinity (f3.5)
- 1963 Jupiter-3 - spot on at 1m and good enough at Infinity (f1.5) - that lense has 2 sets of stop screw holes so someone was already adjusting it
- 1967 Jupiter-8 - spot on at 1m and good enough at infinity (f2)
- 1987 (?!) Jupiter-12 - spot on at 1m and infinity (f2.8)
- 1965 Jupiter-12 - completely off at 1m - this might suggest why lense is in Mint condition
- 1964 Jupiter-8 - completely off at 1m

While this is not statistically significant verification of exact registration distance it already shows that It may be good enough for calibration of completely off lenses. Some of lenses which were tested to be spot on were also giving good results in standard film shooting scenarios.

Used same test setup to adjust shimming in Jupiter-8, photos showing difference before and after (note that these are crops from 24mpix camera)





Additionally I checked actual focus on lense mounted in M39 camera using split prism focusing screen and magnifier:





After checking:
- lense was shimmed to be spot on using Sony and Adapter
- Zorki 4 FSU rangefinder properly measures exactly 1m distance using the lense (i.e. lense distance ring matches result showed by rangefinder patch and that also matches with actual target distance)
- Using focusing screen I checked TTL focus and it was almost spot-on (split prism indicated barely visible split - not sure if I would be able to notice it without magnifying glass) - note that focusing screen here is not at exactly same position as film

Some thoughts:
- after writing with Brian I realized I cannot use this method to adjust FSU lense to work correctly on Leica body
- but I can adjust lense to focus correctly according to its distance scale
- then I can verify if lense distance scale matches with rangefinder in camera
- I verified that most of lenses were spot on with adapter which is a good indication
- TTL focus test proved that focus ended up being at least very close to where it should be (film results will verify)

I'll have to verify results on film but it's already quite promising. It won't give "0.01mm" precision but should be good enough to home-calibrate lenses which were unusable anyway,