Would an electronic rangefinder-lens coupling be relevant?

[younes]

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Having had an M9, but living in a country with no access to Leica services, I got more and more uncomfortable with the rangefinder calibration issue as the number of my lenses grew. I finally sold the M9 and have been using mirrorless cameras since.

 

With growing sensor resolution, the mechanical rangefinder-lens coupling is becoming a serious limiting factor.

 

Now, I was wondering if this could not be solved by replacing this mechanical by an electronic coupling. The position of the rangefinder roller, moved by the rangefinder helix of the lens as the focusing ring is turned, would be electronically measured. This measured position would then trigger the adjustment of the position of the rangefinder patch, for example using a servo or a digitally produced patch in an arrangement similar to the one used in the Fuji X-Pro1.

 

The obvious advantage of this is that no mechanical adjustment or calibration is required. Both RF roller and RF patch would never need to be adjusted after initial build of the camera. All adjustments and calibration could be done via software using a calibration profile for every camera-lens couple. This calibration could even be done by the enduser with the help of an EVF and a software supported procedure.

 

So one would set a calibration profile for every lens he wants to use on his camera, and the camera would upload the corresponding profile every time the lens is mounted. For lenses with strong focus shift, the owner of the camera could also choose at what aperture the calibration is done, depending on his preferences.

 

If this is possible, the list of improvements would be long, among them:

- software calibration allows to perfectly calibrate a camera with an unlimited number of lenses, which is very hard to do with a mechanical coupling

- in the field calibration is possible, with no risk of damage

- as the RF roller is not adjustable, the calibration will not be lost du to excessive vibration or mechanical shock

- focus shift can be taken into account

- etc.

 

Again, if this is possible, one would have the pleasure of using rangefinder focussing without the hassle of maintaining mechanical calibration.

 

If this has already been suggested or discussed elsewhere, don’t bother, but if not, I would be happy to have your opinion about the idea.

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[jaapv]

Why? Retro comparability would be compromised.

I for one would not want to give up my old lenses.

Secondly the whole rangefinder system is mechanical. By making one part electronic (if at all possible) one would be creating problems, not solving them.

[pop]

I think that a further development along this line might be useful.

 

The current RF measures the distance of the optical system from the mount and displaces the virtual images projected by two auxiliary optical systems such that the eye can observe where they overlap.

 

The mechanical solution we all know has indeed a few undesired properties.

 

Separating the measuring of the position of the main optical system from the control of the overlap of the virtual images might indeed eliminate or at least reduce some of the known weaknesses.

 

The accuracy of the measurement of the position of the lens might be a show stopper. I don't know what accuracy we could expect from such a system; I don't know, either, whether that system would be as shock resistant as we would desire it to be.

 

The properties of lenses with floating elements or groups might pose some limitations on the concept as well, though I rather think they wouldn't.

 

The accuracy with which the virtual images can be displaced might be the second show stopper. If this part of the system had to be mechanical as well, shock proofing or frequent recalibration might be issues.

 

I thought of a similar idea not long ago. It was my stereo camera (by Fuji) which made me think of that. This is a pair of two complete small digital cameras in one case, mounted at a distance of roughly seven centimeters side by side.

 

Building those two small cameras into a Leica body at a comparable distance would produce two electronic images which then could be merged into one composite image and displaced against each other according to the position of the camera's main lens.

 

That system would have the obvious drawback that it would produce the image in the finder not optically but digitally.

 

On the other hand, you could achieve all the TO hoped for. In addition, you could zoom the whole finder image, you could move and resize the virtual "RF patch", you could not only move but resize the framelines according to the distance set by the main lens, you could toggle the finder image between the stereo set and the main lens (turning the camera into an EVIL). In a clinch, you even could take stereo pictures of a moderate quality, having actually three cameras in one.

 

The retail price of the Fuji Stereo camera was less than USD 200, IIRC.

[pico]

It might be worthwhile to investigate Linhof's electronic rangefinder. It went to market, but failed. Failures can be informing.

.

[bocaburger]

My M8 focused spot-on with all my lenses, Leica and CV. So did my M9 once I adjusted it myself (came from the factory way out of spec). Both my M240's are spot on. I really don't see a need to fix what isn't broken, especially if it entails adding complexity (and therefore more chance for things to go wrong). Much simpler to hold Leica to their own self-proclaimed superlative manufacture in terms of rangefinder calibration during final assembly and QC. And have the occasional outlier lens brought up to spec.

[pico]

Heck, why electronic? There has been a thing called the Kalart Focuspot for over 60 years. It was first used on the Graflex rangefinder press cameras, then the Rollei, and in 2008 it was modified to use a laser pointer by Ivan Eberle.

 

I put one on the M9. It worked for focusing without framing. It's not what we want, but a new-old point of departure, perhaps.

[younes]

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Thanks to all for your feedback.

 

Jaap, the idea is to remain perfectly compatible with existing lenses. Only the coupling of roller and focusing patch would be replaced. In my understanding, the principle of the rangefinder is to use the parallax effect between viewfinder and rangefinder mirror to determine when focus is achieved. The movement of the mirror induced by rotating the focus ring of the lens has always been mechanical, but I don't see why this could not be done otherwise.

 

I also believe that right choice of components:

- to measure the position of the rangefinder helix of the lens

- to move the rangefinder mirror

could make things easier, not more complex. But maybe I am too confident in the existing possibilities.

[Alberti]

Always fun to think of such innovations.

Another form of hybridism evolves: but

 

First of all,

there must be backwards compatibility. I believe a body that is not compatible with an M-bayonet lens has no future. It would be like a body by Fuji, offering a bayonet of its own.

 

This means old lenses must be usable.

- So, the cam/shaft must be retained.

- So the 'new generation lens' would have to allow the roller/sensor to go to the 0,7 m position (and the finder would then move to the similar out of range frame).

- then there should be some mechanical way to move the cams/levers into position.

 

That could be easy, as a small motor could perform the job of moving it; after being fed with the electronic signal (I guess 10 bits would give enough precision) about the focus, as determined in some way,in the lens itself.

 

The lens electronics and a database with info could well allow to change focus preferences (for the few lenses like the Sonnar where this is applicable) like shown as a benefit in the OP.

 

But really, my M-P focusses the best I ever had in all Leica bodies. Need i.m.h.o.: zero.

 

Why then?

1. Would it allow cheaper lenses? Yes some have complex double helixes specifically to activate the RF cam (to achieve stellar focussing performance).
   
2. Would it allow a "zoom"? yes, as the frame become equally electronically activated, frame selection can also be set to any position and not be dependent on the flange. Also, this would work for non-conforming lenses re the flange detection with just three positions: a hypothetical new 40mm would have a precise frame of its own.
   
3. Would it allow electronic sizing of the frame window? Yes, because the presented frame line would allow to size it not at a fixed distance (M8: 1m, M9, M: 2m) but scaled continually as required by the actually cozen focus point. This means: also a precise RF-shift movement can be supported.
   

 

however

• point 3 above can also be obtained if the distance capturing of the lens is done in-camera.
  

 

I suggest Leica does adopt point 3 as elucidated in the bullet.

[mjh]

The position of the rangefinder roller, moved by the rangefinder helix of the lens as the focusing ring is turned, would be electronically measured.

It already is. There is a Hall effect sensor in the M and M-P (Typ 240) that triggers the focus-assist feature in live view mode when an M lens is attached – that is how the camera knows you are trying to focus. Whether this sensor offers the necessary resolution and precision to be used in the way you envision is a different matter. Anyway, between the M9 and M (Typ 240) Leica has spent a lot of effort to improve the opto-mechanical rangefinder and I doubt they intend to replace it anytime soon. At least that was the impression I got from talking to Leica’s rangefinder specialist (see “Rangefinder Anatomy”, LFI 1/2015).

[Hey You]

Don't dispense with the manual rangefinder.

Instead, add functionality which complements it.

If Leica puts a position sensor on the arm in the M9 body which follows the lens's focussing cam, the camera's CPU now knows the distance at which the lens is focussed. LED framelines can then adjust electronically to indicate the exact dimension of the image at this focus distance. At present the framelines, being mechanical, are approximate.

Let's go a bit further. The present Leica M system cannot accommodate zoom lenses.

If an electronic contact were added between the lens and (future) M bodies, the camera's CPU would not only know the distance that the lens is focussed upon, but also the zoom setting. LED framelines could adjust to reflect both distance and zoom.

What is significant about all this is that the manual rangefinder persists. Only the framelines become electronic, and the initial step toward this occurred with the M240's abandonment of manual framelines.

All legacy lenses would continue to work seamlessly on new M bodies, but there is significant additional functionality for new lenses, and possibly zoom lenses.

Just my wild guess . . . .

[timde]

Yes, this is possible. The mechanical link is replaced by a digital sensor and an actuator for moving the rangefinder patch. Nothing else changes.

 

The significant benefit IMO would be that focusing could be calibrated by the camera owner using the Live View. No more sending cameras back to Leica. So ... perhaps Leica would not be so interested in that, or perhaps they would?

 

In any case, I was wondering about the Zeiss Loxia that I have ordered and still await. Its the modern incarnation of a Manual Focus lens. On the premise that Zeiss have a Film Rangefinder design, and a good partnership with Sony, I wonder if they might have some interesting ideas for the future. Any new "Rangefinder" camera using a "Digital" Manual Focus lens would need an actuator to move the rangefinder patch ... and an M-mount adapter with the correct electrical interface could also work with that.

[indergaard]

Anything that can improve the reliability is welcome in my opinion. The mechanical rangefinder calibration is more of a thorne in the side than something I am greatful for. Over the course of the last 3 years my M cameras has spent in total over 6 months in service for rangefinder calibration. I would gladly want something that is more reliable, be it electronic or anything else, as long as it works and works and works and works reliably (which the current mechanical rangefinder doesn't).

[CheshireCat]

EVF + per-pixels phase detect sensors will solve this problem for good in the near future.

The RF did a good job for 100 years. Time for it to retire and enjoy the remainder of its life in some nice exotic place

[pico]

[...] On the premise that Zeiss have a Film Rangefinder design, and a good partnership with Sony, I wonder if they might have some interesting ideas for the future. Any new "Rangefinder" camera using a "Digital" Manual Focus lens [...]

 

Presuming there is a significant market for yet another rangefinder film camera.

 

Do I hear gales of laughter coming from Wetzlar?

[jaapv]

Not really. Leica is well aware that Zeiss made a decision not to try and compete in 2008. In the meantime they are concentrating on lenses and have lost all interest in rangefinder bodies, digital, film or otherwise. At Photokina they were displaying their lenses on M240 cameras.

[jaapv]

EVF + per-pixels phase detect sensors will solve this problem for good in the near future.

The RF did a good job for 100 years. Time for it to retire and enjoy the remainder of its life in some nice exotic place

 

The exotic place being the big world outside Silicon Valley I suppose...

[jaapv]

Anything that can improve the reliability is welcome in my opinion. The mechanical rangefinder calibration is more of a thorne in the side than something I am greatful for. Over the course of the last 3 years my M cameras has spent in total over 6 months in service for rangefinder calibration. I would gladly want something that is more reliable, be it electronic or anything else, as long as it works and works and works and works reliably (which the current mechanical rangefinder doesn't).

 

Weird. I have a an M8, M9, M240, MM, M3,M4,M6. None have gone out of calibration spontaneously over the years -forty of them- and the times that it happened due to a hefty bang average adjustment time was less than a week, with the record being 30 minutes when I dropped an M8 on concrete within a short distance of Will van Manen's workshop

[mjh]

EVF + per-pixels phase detect sensors will solve this problem for good in the near future.

That’s rather doubtful. Phase-detection pixels don‘t work that well with low light as they are less sensitive than dedicated phase-detection AF sensors in DSLRs – mirrorless cameras phase-detection pixels in combination with contrast-based AF since they could not shoulder the burden alone. Also phase-detection pixels, just like dedicated phase-detection sensors, don’t like stopping down. Even when there is plenty of light, phase-detection requires the aperture to be wide open. There may a place for on-sensor phase-detection to complement focus indicators such as focus peaking, but it won’t be a replacement for the rangefinder.

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Hallo,

Look here: Leica M

[CheshireCat]

Phase-detection pixels don‘t work that well with low light as they are less sensitive than dedicated phase-detection AF sensors in DSLRs

[...]

Even when there is plenty of light, phase-detection requires the aperture to be wide open.

 

Not at all.

 

As per Canon specs:

[Dual Pixel AF] allows the use of high precision phase-detection autofocus in live view, functional across 80% of the frame down to 0 EV and f/11.

 

Back to the RF, I find it unusable in low-light, unless there is a very visible pattern (for the human eye) near the focus point.

[CheshireCat]

The exotic place being the big world outside Silicon Valley I suppose...

 

Resistance is futile. You will be assimilated.