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Focus adjustment Odyssey


jpk
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Does your rangefinder patch converges at infinity? (focus on a star).

 

Did you completely read my first posting...?

 

Did your 90/2 apo have 6-bit coding when you purchased it? Just to know it it has been calibrated for digital.

 

Yes, it was coded. But the initial problem with the lens was different as I mentioned in my initial posting...

 

You know that the rangefinder is at its accuracy limit when 90mm lenses are open at f/2

 

My sample shot shows meters of front focus, that has nothing to do with the limits of the rangefinder!

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My M8 was faultless from start to end.  My M9, bought new, arrived with a badly miscalibrated rangefinder.  Not merely the infinity adjustment, the sweep (arc, gain) was off also.  Rather than kiss my expensive new camera goodbye for months and chance it might still return imperfect, I adjusted it myself.  It remained in perfect adjustment for the remainder of time I owned it. 

 

Both my M240's (one demo, one pre-owned certified) have been perfect from the start. 

 

I have a couple dozen lenses, the newest of which dates from 1994, so all pre-date FF digital by a decade to several decades.  Some are screw mount, some are C/V, one is a Nikkor.  Some are fast (eg an '80s 50 Lux, 90s pre-asph 90 Cron).  Of all of them I have had focusing issues with only two.  One was my 50 Summicron 11817 "tabbed", which I sent off to a private repair person who adjusted it perfectly.  The other was my 135 T-E, which the repair person was unable to adjust properly.  So I took measurements and machined the case of the optical cell so it was closer to the focal plane by the precise amount needed to focus perfectly. 

 

The OP's litany of defects does seem excessive.  If I had that many bad experiences with Leica I would have sold the lot and been done with it. 

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Ah ! ....... another lucky soul with 'miscalibration' problems .......   threads abound here with this and similar tales of woe.

 

As a longstanding 'calibration perfectionist' I have learned the following lessons:

 

1. Most Leica bodies arrive 'adequately' .... but not perfectly calibrated ....... the M240/246 are generally better adjusted than previous cameras.

 

2. Most Leica lenses are perfectly calibrated ...... but those with floating elements are often out as they are difficult to do accurately.

 

3. The more lenses you have ..... and the more bodies you have, the less likely they are all to be perfectly adjusted with regard to each other. 

 

4. Lenses with focus shift are a real problem and calibration is a compromise and may not be perfect for all distances/apertures.

 

5. The best you can achieve with multiple lenses and bodies is most of them being OK most of the time in most situations.

 

6. If you want the camera adjusted properly to suit your own lenses it is better to do it yourself. You can then decide on your own level of accuracy and Quality Control with regard to adjustment.

 

7. Only by trying adjustment yourself will you realise just what Leica is up against trying to get this antiquated RF mechanism to the accuracy needed for a digital camera and complex optics. 

 

Of course you can always take photos at >2m and use f5.6 and above ....... and then you will very rarely have any issues ....... or stick to the EVF on the M240. 

 

...... oh ... and the 90/2 apo was one of the few lenses I got rid of due to focussing issues ...... equivalent to the Noctilux in the degree of accuracy needed ...... but clearly not assembled with the same degree of care. Get a 90/2.8. I have been tempted to get a 75/1.4 ...... but suspect it will all end in tears for similar reasons ........ so have (so far) resisted......

Edited by thighslapper
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[...] the 90/2 apo was one of the few lenses I got rid of due to focussing issues ...... equivalent to the Noctilux in the degree of accuracy needed ...... but clearly not assembled with the same degree of care. Get a 90/2.8 [...]

 

My 90/2 apo is spot on and my 90/2.8 needed calibration. C'est la vie...

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Depends on aperture and focus distance of course. How long was the latter? 

 

40 meters wie open.

 

Sorry. I interpreted your rangefinder patch to be off in the vertical direction...

 

If the patch is off in vertical direction how can it converge at infinity...?

 

Rather than kiss my expensive new camera goodbye for months and chance it might still return imperfect, I adjusted it myself.

 

Wow! Did you also calibrate the sensor plane?

 

Lenses with focus shift are a real problem and calibration is a compromise and may not be perfect for all distances/apertures.

 

I can deal with focus shift.

 

The best you can achieve with multiple lenses and bodies is most of them being OK most of the time in most situations.

 

I just made some tests and everyting is fine EXCEPT the Apo-Summicron 75: this lens is fine on the Monochrom, but on the M type 240 it is off in the middle to far distance. At short distances it focuses as it should. All other lenses are fine on both cameras. Sounds not logical to me... So you say that this is as good as it gets?

 

Of course you can always take photos at >2m and use f5.6 and above

 

I think I will have to remember to use the Apo-Summircon 75 on the M type 240 at middle to far distances only stopped down or with LV

Edited by jpk
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My Apo 75/2 has been back to Solms/Wetzlar twice to get it right .... again I suspect the floating element design is the cause ......

 

The main problem with multiple lenses and bodies is trying to work out which are the rogues ...... I ended up with a complex spreadsheet annotated with the accuracy at near, mid and infinity for each lens and body combination. Even then there were some anomalies that seemed to follow no logical pattern ...... but at least it conformed which lenses were significantly out and which body was definitely well adrift of normal. 

 

It's one reason why I changed from the old Monochrom to the M246 ...... at least with focus peaking and liveview you can be very clear what is going on and makes adjustment much quicker. 

 

Vertical adjustment is often off ....... put a magnifying eyepiece on and you will soon find out .... and is often a cause of a less than crisp image even when the RF is aligned properly .... again easily self adjusted. 

 

Adjustment has nothing to do with the sensor ....... just the offsets in the RF mechanism via an eccentric roller (infinity) and roller lever length (near) .... these are just inside the lens mount on the body and easily accessible. 

 

Just needs an allen key, screwdriver, logical mind and patience. 

Edited by thighslapper
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If the patch is off in vertical direction how can it converge at infinity...?

 

A star would look like a snowman or stoplight. Convergence along the horizontal axis but misaligned in the vertical

 

Again. Good luck

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Adjustment has nothing to do with the sensor

 

OK yes, BUT ONLY if the sensor is in the correct position. Otherwise the sensor also needs adjustment.

 

A star would look like a snowman or stoplight. Convergence along the horizontal axis but misaligned in the vertical

 

As I wrote earlier the patch was either off vertically or the focus was off. In both cases focusing is not a joy...

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The sensor position is laser(?) aligned to the lens flange to within a thousandth of a mm and is hardly ever the cause of the problem. It is the one thing that Leica can check quickly and very accurately. 

Accurate adjustment of the RF mechanism is another story completely .....   as is adjustment of some of the more complex Leica lenses ......

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Depends on aperture and focus distance of course. How long was the latter? 

40 meters wie open. [...]

 

OK so you've got about 5 meters of DoF at f/2 with your 100% crop. The least focus variation could explain your problem as i suggested above. May come from the lens, the body, and/or yourself, i don't know. What is sure is your digital rangefinder has a 0.68x magnification and is not as accurate as the 0.85x you were used to with your film body. My best advice would be to send in your lenses and bodies separately if you own several of them and to use a diopter corrrection lens and/or a magnifier when you shoot difficult lenses like 135/3.4, 135/4, 90/2 or 75/1.4 at full aperture if the EVF is not your cup of tea.

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My best advice would be to send in your lenses and bodies separately if you own several of them

 

Again...? The Apo-Summicron 75 is the only lens still mis-focusing in the middle/far distance, but only on my M type 240. On my Monochrom it focuses fine. All other lenses focus fine on the Monochrom AND on the 240. I can't imagine any explanation of this!

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I thought that you had focusing problems with your 90/2 apo but now you state that all your lenses but your 75/2 do focus fine on both your MM and M240. Bit confusing to me sorry. If you sent your 75/2 in together with your MM it is not surprising that it focusses well with the latter but it is also possible that you have now problems with other bodies. To avoid that, i always send my bodies and lenses in separately personally. YMMV.

 

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Again...? The Apo-Summicron 75 is the only lens still mis-focusing in the middle/far distance, but only on my M type 240. On my Monochrom it focuses fine. All other lenses focus fine on the Monochrom AND on the 240. I can't imagine any explanation of this!

 

...... the RF adjustment is very crude and it is difficult to get it 'exact' ...... only to a range of tolerance.

 

With distance adjustment you have to contend with the large DOF that occurs the closer you get to infinity ..... so this is less critical than the near adjustment where DOF at 0.7m may only be <1cm with the lens wide open and the misadjustment very obvious when you check images to see if it is ok.  

 

If you have the distance adjustment on the RF mechanism slightly off it may make no difference in practical terms for most lenses ..... except with the one lens that is slightly misadjusted in the other direction ..... so the additive effect of the errors then becomes obvious. 

 

Because of his  element of tolerance in the RF adjustment due to DOF I tend to use my 135/3.4 to check it for distance ...... it isn't a complex lens and there are rarely any complaints about this lens turning up poorly calibrated. If the adjustment is ok for this then it is usually fine for all my other lenses. 

 

Live view does not lie ......... compare manual focus versus focus peaking with the M240 with the camera on a tripod ....... if the other lenses are fine and the 75/2 is still misbehaving when used on the RF then send it back for adjustment .... it can really only be the lens that is at fault ..... and eventually they will get it right .......

Edited by thighslapper
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This is a sobering thread about the rangefinder mechanism.   Leica has said they are not abandoning it but is it not true that

(1)  Optical rangefinder can only be adjusted to a certain degree and difficult to do across a wide range of lenses.

(2)  EVF or LV is helpful in adjusting;  this cannot be true if the EVF is less accurate than the RF

 

So why would not Leica want to try to figure out a way to keep the essentials of the OVF advantages (brightness, see outside the framelines) while improving the accuracy with some form of digital focus verification?   If the focus mechanism resides on the sensor, why would this not be possible?   I'm not talking about autofocus, just a digital rather than optical focus aid.  Maybe something digital to supplement the OVF even if not a substitute?  

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I thought that you had focusing problems with your 90/2 apo.

 

Sorry to confuse. I uploaded the Apo 90 sample just to illustrate the amount of mis focus. I sent in my complete gear, it came back with the 90 focusing fine but the 75 still off...

 

the RF adjustment is very crude and it is difficult to get it 'exact' ...... only to a range of tolerance.

 

...But on my MM the 75 focuses fine!

 

compare manual focus versus focus peaking with the M240 with the camera on a tripod

 

That's what I did...

 

So why would not Leica want to try to figure out a way to keep the essentials of the OVF advantages (brightness, see outside the framelines) while improving the accuracy with some form of digital focus verification?   If the focus mechanism resides on the sensor, why would this not be possible?

 

It should be even possible without changing the system: measure the focus plane automatically, calculate the correction curve and apply it with CNC to the focusing helical or to the part which pushes the cameras RF-mech. This would allow to adjust each lens individually AND automatically...

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It should be even possible without changing the system: measure the focus plane automatically, calculate the correction curve and apply it with CNC to the focusing helical or to the part which pushes the cameras RF-mech. This would allow to adjust each lens individually AND automatically...

I'm not an engineer so I have no idea of whether this is feasible.  Something in addition to the hard to adjust optical rangefinder mechanism would be welcome.

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[...] I'm not talking about autofocus, just a digital rather than optical focus aid. [...]

 

We have both digital and optical aids with the M240 already. The next ones, at least the digital one, should be even better.

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