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135/f3.4 APO M lens 6-bit code question


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1. "Advanced" and "Leica M" are mutually exclusive concepts. ;)

 

More seriously - yes, Leica had to, and wanted to, make their digital cameras as backwards-compatible as possible to lenses designed for film decades ago. They know their customers. So they did not design a system that required chips in the lenses (for how can one fit a chip or a resistor into a 1980 35mm lens designed for film?). Leica will never put electronics into their M lenses (if you want that, buy an S or an SL or a TL). And yes, that means M lenses will never: be auto-focus; transmit aperture used; or transmit the focus setting.

I fully understand that approach. The question to answer is: backwards-compatible of what? New lenses for old bodies? Or old lenses for new digital cameras? If we take into account assumption that 6-bit code is important for quality of M10 images old lenses are not backward compatible for M10 body. New lenses are compatible for old cameras but please tell me - what is the difference between electronic based and optical based 6-bit coding system from the old camera point of view? If you have a chip in lenses it does not mean that you have to use it. As old camera is ignoring 6-bit coding now (based on optical reader) it may also ignore gold electronic contacts on the same way. I don't ask for AF and servo engine in the lenses. I am very much happy with MF as I am using that very often with AF equipped cameras. But value of aperture is important in my workflow and frankly speaking I do not see a serious reason to do not equip new lenses with such a passive feature. Maybe Leica knows their customers -as you wrote. But all of them? They take care very deeply about preinstalled base of users. What about new customers? Do I really want a lot asking for aperture value in EXIF file? If yes - what one may say about the wish list as follows: https://www.l-camera-forum.com/topic/273822-m10-the-game-changer/?

 

From time to time I use Contax G2 for film. And I "have full EXIF data" printed on small distances between frames. So - if someone was able to do that on regular film years ago the small and silent request like my should be not treat as revolutionary approach :-)

 

 

 

2. The "module" that does the important corrections is the camera firmware and the camera's main CPU. For either RAW or JPEG. Additionally - Adobe may provide adjustments for lens distortion, and/or color aberrations, through their software recognizing the passive lens ID.

 

 

OK. if Leica firmware make all necessary corrections why LR is correcting on visible way already properly corrected images? 

 

4. As to M lenses made by someone other than Leica (e.g. Voigtlander, Zeiss) - frankly, that is not Leica's problem. They are an optics company in business to sell lenses (for which they provide cameras). They are not in business to sell cameras that take other manufacturer's lenses. As it happens, as lct says, there are some workarounds to use 3rd-party lenses on a digital M, if one must. And - again - it really only matters for wideangle lenses. A Voigtlander 50 or 75 or 90 will function quite well on a digital Leica, without 6-bit coding.

I did not say that this is Leica problem. This is my problem. You mentioned about CANON. This is not CANON problem  to support SIGMA lenses but they are supported. I don't use Voigtlander 50+ lenses but 50- lenses and my problem in fact is not to have 6-bit coding on them but to have name of lenses included in EXIF file instead of "R-Adaper M" general purpose name

 

Add 3. - thank you for details. From the 3D perspective you are perfectly right. But 2D corrections still remains on the table.

 

 

Indeed the EXIF data of digital M gives an information about aperture... but is just an "estimate"... there is a front sensor which measures the light, and given that camera does know the exposure time used, it can compute (and record) the aperture : I have been always amazed that Leica did introduce an additional component just to provide an information that, many times, is far from trustable (it's lot of time that I even don't take note of it... should it be absent, would be the same for me).

Anyway... let's say that they did something to overcome the intrinsic limitations of their system... M system is what IS and USED TO BE : as pointed by Adan, backwards compatibility is one of the main points that keeps us faithful in the brand...

I am more than happy that I don't have such an estimation on my M10. It is better to have empty field than data from the sky.

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1. Old lenses are indeed forward-compatible for use on digital (up to a point). Leica can and will ADD the 6-bit coding to older lenses (roughly back to 1980, and a few even earlier than that.) You send the lens to Leica, and Leica replaces the chrome mount ring on the back with one that has the coding. Just as Nikon would, for a time, retrofit pre-1977 Nikkors with the new "AI" mechanical lens link after they introduced that change.

 

And note that that does not require making room for a chip (for which there is very little room inside an M lens - they are very tightly engineered with little space left over for electronic gizmos.) A few painted spots on the back for the critical lens ID is much less "invasive" than gutting the lens to install or make room for electronics.

 

Here's a cross-section of a Leica 50mm Summilux ASPH - you draw me a diagram of where, in that solid mass of brass, aluminum, and glass, you would put a chip, and sensors for aperture ring setting, and focus setting, and the flex-cable to connect them to a set of contacts on the back. http://blog.wanken.com/wp-content/uploads/2011/11/leica-lens-cutaways-03.jpeg

 

Here's a cross-section of a Canon prime lens (400mm) - basically a "shell" or space-frame with the lens elements floating in the middle. http://www.stevestenzel.com/photos2013b/cross_section_08.jpg

 

A "hollow" lens structure makes a lot of room for electronics. BTW, the Contax G lenses are like that also: a titanium shell, with the glass floating inside, instead of a solid block of layered metal. So are the Leica SL lenses, to some extent (although with more metal and less polycarbonate plastic) - but that is simply not how Leica wants to engineer the M lenses - different product, different values.

 

So, compared to electronics, the 6-bit optical coding is easier to retrofit to older lenses, making them forward compatible. It was easier to add (on the fly, in 2006) to the construction of new lenses already designed and on the factory floor. It will be easier and less complex to install in future lenses.

 

2. Lightroom (or Adobe Camera Raw, for those of us using the full version of PhotoShop) is making DIFFERENT corrections than Leica does in the camera. LR corrects distortion and color aberrations; Leica in the camera corrects the vignetting and color vignetting. Totally different things, that are not duplicative. You can add LR's own vignetting corrections as well, if you like.

 

3. As to third-party lenses and coding: There are solutions to getting the most important function done - correcting the color distortions from wide-angles. Paint on some black marks. Get the lens mount machined with pits so that the black paint lasts longer with use (Voigtlander has already started machining in a channel in their newer lenses with native M-mounts). As to the name of the lens in EXIF - we're all out of luck. Only Leica lens names are available, even with coding. Personally, I am not troubled that all my (coded) Voigtlander 15mm pictures come up as "Leica 16-18-21mm @ 16mm" in EXIF - what's the big deal?

 

I guess I see getting the name of a lens in EXIF as a "fly-sized" problem - somehow millions of photographers took great pictures throughout the 20th century with no EXIF at all. A fly-sized problem is not worth totally gutting all the M lenses in existence to rearrange them for a different ID system.

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I did not say that this is Leica problem. This is my problem. You mentioned about CANON. This is not CANON problem  to support SIGMA lenses but they are supported. I don't use Voigtlander 50+ lenses but 50- lenses and my problem in fact is not to have 6-bit coding on them but to have name of lenses included in EXIF file instead of "R-Adaper M" general purpose name

 

 

 

 

Actually, Canon do NOT support Sigma lenses, they tolerate them to an extent. The EF mount is NOT open, just like the F mount, it is closed (although I presume the original F mount patent has expired). 3rd party lens manufacturers have to reverse engineer the physical and electronic connections. Nikon goes a step further than Canon, often changing the F mount contacts to render 3rd party lenses less compatible, so I suppose Nikon do not even tolerate 3rd party manufactures.

 

The M mount is not open, it is just a patent that has expired allowing other manufacturers the chance to make lenses that fit perfectly. The date the patent expired just happened to be about the time when Voigtlander and Zeiss started making M mount lenses - before this time Voigtlander made thread mount lenses, the patent having expired long ago.

 

As far as I know the only open mounts, where 3rd party manufactures get all the info are the M43 mount and the FE (Sony) mount.

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/snip/

 

my problem in fact is not to have 6-bit coding on them but to have name of lenses included in EXIF file instead of "R-Adaper M" general purpose name

 

/snip/

 

It is better to have empty field than data from the sky.

 

So treat "R-Adapter M" as an empty field and all is well! :D

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Andy - first of all thank you for so detailed explanations. I very appreciate your effort

 

1. Old lenses are indeed forward-compatible for use on digital (up to a point). Leica can and will ADD the 6-bit coding to older lenses (roughly back to 1980, and a few even earlier than that.) You send the lens to Leica, and Leica replaces the chrome mount ring on the back with one that has the coding. Just as Nikon would, for a time, retrofit pre-1977 Nikkors with the new "AI" mechanical lens link after they introduced that change.

 

And note that that does not require making room for a chip (for which there is very little room inside an M lens - they are very tightly engineered with little space left over for electronic gizmos.) A few painted spots on the back for the critical lens ID is much less "invasive" than gutting the lens to install or make room for electronics.

 

[...]

 

So, compared to electronics, the 6-bit optical coding is easier to retrofit to older lenses, making them forward compatible. It was easier to add (on the fly, in 2006) to the construction of new lenses already designed and on the factory floor. It will be easier and less complex to install in future lenses.

 

 

I am not quite sure but old lenses are not forward compatible but have possibility to be. Is Leica offering 6-bit code add-on for free or you have to pay? I think that you have to pay - what means that you may purchase compatibility. I really don't have anything against that conservative approach but it doesn't mean that there is no way to produce new lenses equipped with extremely small aperture reader and to find (or setup) 1mm room for it.

 

 

3. As to third-party lenses and coding: There are solutions to getting the most important function done - correcting the color distortions from wide-angles. Paint on some black marks. Get the lens mount machined with pits so that the black paint lasts longer with use (Voigtlander has already started machining in a channel in their newer lenses with native M-mounts). As to the name of the lens in EXIF - we're all out of luck. Only Leica lens names are available, even with coding. Personally, I am not troubled that all my (coded) Voigtlander 15mm pictures come up as "Leica 16-18-21mm @ 16mm" in EXIF - what's the big deal?

 

I guess I see getting the name of a lens in EXIF as a "fly-sized" problem - somehow millions of photographers took great pictures throughout the 20th century with no EXIF at all. A fly-sized problem is not worth totally gutting all the M lenses in existence to rearrange them for a different ID system.

 

I am not going do die for missing lens name in EXIF and will continue to use M10 with pleasure. Why I want to have real lens name in EXIF file instead of fake? Because it is important for my LR workflow. LR automatic lens profile correction is based and dedicated on true lens name. I browse LR database on lens name. I have also some LR macros based on lens name as parameter. Of course - I have still possibility to make great picture with M10 without that feature. And I am still waiting for my best picture ...

 

"Fly-sized" problem depends on someone needs. We may really go through the list of M10 features and ask why some of them are available? Is LV important and necessary? I may say - it is useful from time to time and necessary for mobile app. For example, you may use it as focusing tool for EOS lenses connected to M10 via M/EOS adaptor. But for huge amount of people it is just useless.

 

I am nothing more but photography enthusiast and amateur for over 50 years and still number of my photos made on film is very large in comparison to digital pictures. However, I have been also working with computers for over 35 years and I am very glad that EXIF can maintain the image data - instead of writing them on a piece of paper - as I did in the case of the traditional film hundreds of times. 

 

 Thanks

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[...] Why I want to have real lens name in EXIF file instead of fake? Because it is important for my LR workflow. LR automatic lens profile correction is based and dedicated on true lens name [...]

 

You are not alone but M lenses are 100% manual and have always been so. They have no motor nor electrical contact as you know. Only way to keep them as small as possible IMHO. Some of us are yet complaining about current M lenses being more bulky than their predecessors. They/we would prefer no compromise at all on size and weight over any non-optical consideration. YMMV. 

Edited by lct
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