Calibrating Summilux 50/1.4 pre-asph for M9?

[brusby]

JC, I'd be happy to do the test at another distance if you'd like.

 

[jcm0]

very narrow band of focus in front, and much more in focus behind the object I was focusing on. This might be good for landscape shots, but I've been doing more informal portraits, and for that I'd much prefer if the situation were reversed, i.e., with the thing I'm focusing on at the back of the focal field. That way, if I'm focusing on someone's eyes, they would be the last thing in focus which would throw the ears and the background more out of focus, kinda like the way traditional large format portraits looked.

That is exactly my opinion

I think a practical solution for someone like me might be to have the lenses optimized or collimated at one stop more closed down than the maximum aperture.

Can you explain a bit more ? Sounds interesting Did you mean "one inch" instead of "one stop" ? If you mean "one inch", I agree, but I am not sure if this can be done by tweaking the lens . Anybody has an answer to that question ??

Or maybe my rangefinder in the camera is off a bit and needs adjusting.

Probably another variable to take into account with focus shift and lens tuning ...

 

[jcm0]

JC, I'd be happy to do the test at another distance if you'd like.

Brusby, I would be great.

I have done your test at different apertures and different distances, but this as soon as the aperture is smaller than 2.8 or the distance > 1m, the point of focus is very difficult to determine and these second tests are not perfectly consistent. I'll will have to repeat my tests to get more consistent results.

Anyway what I have seen is that at any distance the point of focus is fairly in focus, but it is not the point of best focus, and the area of DOF is not generaly centered on the point of focus which make the focus point appear as missed (the delta of focus is from 1 to 2.5 centimeters). 1 to 2.5 centimeters of focus error impacts a lot the sharpness of the picture at the point of focus.

I am not sure this is a problem of my M9 rangefinder alignement, as I have the 35 lux FLE which is on focus with my camera (maybe I should verify this point again).

Let me know what you find !

Regards,

JC

 

[jcm0]

Hi there,

Here are some more findings.

Leica Solms confirmed that my lens was tested at all distances. This means two things: My M9 rangefinder is a bit off + taking into account that there is a focus shift that's means that the lens was well calibrated ... to a given aperture (probably f1.4 but not sure).

I have done my tests for the third time. I consistenly see the following things:
- at any distance and any aperture the point of focus is fairly in focus, but it is not always the point of best focus (which is important because it makes appear the focus point as missed).
- from f2.8 and above (tested at f2.8, f4, f5.6) there is no focus shift ie no shift of the real focus point (the point of best focus) when changing the aperture, at any distance (tested at 0.7, 0.8, 1 , 1.2m) . However with my lens/camera, there is a focus error of about +2.5cm (post-focus) at any distance(tested at 0.7, 0.8, 1 , 1.2m)/diaphragm(tested at f2.8, f4, f5.6) , which is usable below 1m and unimportant farther.
- there is a focus shift below f2.8 (tested at f2, f1.4). From 1m it is unimportant for me as the real focus point is before the point of focus and the focus area is larger and increases when the distance increases.
- the real tricky focus is at below f2.8 at less than 1m. With my M9 camera the point of best focus appears be from 1.5 to 2.5cm after the point of focus, which lead to unpleasing effects on a portrait where the focus is made on the eyes. This focus error may be at 70% linked to my M9 rangefinder misalignment. That's the reason why I am interested to read someone else measurements to compare with my findings. Anybody ?

Regards,

JC

 

[Ronald M]

The is nothing to be done for focus shift as it is part of the lens design. You can optimize it any stop you wish, but that will be the only correct one. The newest lenses have designs that minimize or eliminate focus shift as f stop is changed.

If it is off at all stops, then a repair is in order.

 

[ferider]

I fear you have missed the meaning of the word "tolerance" in technical jargon. It means the limits of the spread of acceptable adjustments. Which is more narrow on a sensor than it was on film. So some - but not all- older lenses need to be adjusted within the new tolerance range to be accurate on a sensor. Obviously that will not affect their usability on film, as a matter of fact it may be improved.

As an engineer, I do understand manufacturing "tolerance".

The facts are:

1) The focusing tolerance that the Summilux was built to is very different from the Leica M9. So there is no "standard", since standard requires documentation of tolerances of at least 2 products at the time of manufacturing.
2) We still haven't heard from Alex how much "shift" he observes.
3) The Summilux indeed has observable shift, also noticable on film.
4) We are talking 50/1.4 with minimum focus of 1m here, not, say, a 75/1.4 Summilux.
5) In contrast to many of you, Alex wants to use his lens on both digital and film bodies. The standard M9 user answer, "you have to send both to Solms for calibration" just doesn't apply here.

What triggered my previous answer was the statement that one shouldn't "botch" Leica focus adjustment DIY, but have the factory do it instead. Part of the strength of Leicas in the past was possible adjustment in the field, when RF alignment just can go out of whack ... nowadays, having to wait several months for the factory to align an RF is just ridiculous for a camera to be used other than for jewelery.

Roland.

 

[Alex Krasotkin]

Guys, apologies for not writing earlier due the busy days....(( Maybe you can find this answer rather stupid, but anyway...after many years of shooting only film, I became too badly careless re shooting information, which obviously is unavalible on M film bodies. Most of my focus shift pics on M9 were made with 1/15 -1/24 shutter speed, where the focus shifted materialy. Again I have got used to film bodies like M6 anm M7, which handle 1/15 easily. Now I understand that I have to be extremelly carefull with shutter speed on M9. The real focus shift I will test during coming weekend and report my findings here.
Alex