Newbie Question - Please Clarify 6 Bit Coding

[behirsch]

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I have been following the various threads on 6 bit coding but I still have a few questions.

 

1) Does the exif data give the lens name, such as "35mm Summicron", or a more general description such as "35mm f2." If it has Leica's trade names it would be confusing to have another brand lens coded, because the exif entry would be wrong.

 

2) Since the lens corrections for different noncoded lenses of the same focal length and aperture won't really be the same, can I always assume they will be close enough and better than nothing?

 

3) Has anybody tried the LTM to M adapters from Europe, sold on eBay, with grooves already milled?

 

4) Has anybody tried the mounts, also sold on eBay, which replace the existing rear part of the Leica lens mount but which come with grooves milled? According to the eBay posting all one has to do is get the mount for the correct focal length and the right number of screw holes, and do a quick exchange.

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[01af]

Do the EXIF data give the lens name, such as "Summicron-M 35 mm", or a more general description such as "35 mm f/2"?

When a coded lens was used, the EXIF data of the files out of the camera contain no lens information besides focal length and lens speed. The Maker Notes data contain the 6-bit lens code and the 2-bit frameline code. That's it.

 

If you see a lens name displayed then that's an interpretation of the lens code, provided by the image processor or image viewer you're using.

 

 

... it would be confusing to have another brand lens coded

Codes for non-Leica lenses don't exist, and they never come coded. As simple as that. So no confusion possible. If you decide to disguise your Voigtländer or Zeiss lens as a Leica lens then that's your business.

 

 

Since the lens corrections for different noncoded lenses of the same focal length and aperture won't really be the same, can I always assume they will be close enough and better than nothing?

No, you can't. Usually it's close enough and better than nothing indeed. But you cannot safely assume it will be always that way.

 

 

According to the eBay posting all one has to do is get the mount for the correct focal length and the right number of screw holes, and do a quick exchange.

After changing the lens' bayonet mount at home, you cannot safely assume the flange distance and the centering will still be perfect. You may be lucky, but you may just as well end up with a screwed-up lens (pun intended ).

[farnz]

... 3) Has anybody tried the LTM to M adapters from Europe, sold on eBay, with grooves already milled? ...

I'll assume that you're referring to the brass ones produced by John Milich (in NY) because I haven't seen any others. They're very well made and milled from solid brass and providing that you choose suitable paints for coding the slots they perform very well.

 

Pete.

[mjh]

Does the exif data give the lens name, such as "35mm Summicron", or a more general description such as "35mm f2."

It is neither; rather the lens code itself gets stored. Of course the lens code uniquely identifies the lens so an application may map the code to the name of the lens. If you have been coding a non-Leica lens as some Leica lens, the name displayed will be wrong since the code was wrong to begin with.

 

Since the lens corrections for different noncoded lenses of the same focal length and aperture won't really be the same, can I always assume they will be close enough and better than nothing?

That is (more or less) true for the M8, but not for the M9.

[behirsch]

Thanks for the explanations. They are very helpful.

 

Regarding the 6-bit adapter, the one I saw on eBay was not made by John Millich. It is imported from China. In the last couple of days three more suppliers have posted ads, one from China without a brand name, one from California marked "Jieying.", and another Chinese seller of Kipon adapters.They are all US$40-50.

 

Bruce

[farnz]

Thanks for the explanations. They are very helpful.

 

Regarding the 6-bit adapter, the one I saw on eBay was not made by John Millich. It is imported from China. In the last couple of days three more suppliers have posted ads, one from China without a brand name, one from California marked "Jieying.", and another Chinese seller of Kipon adapters.They are all US$40-50.

 

Bruce

Bruce,

 

I don't 'know' these but be a little wary because the rear lens element to sensor distance needs to be very accurate. Some of the (non 6-bit) LTM to M adaptors from China may not be the right thickness and I recall reading complaints about resulting focussing problems. But if you find that they work, then they work.

 

Pete.

[ho_co]

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Bruce--

As Pete says, don't scrimp on the quality of the adapter.

 

Leica used to make them, so you can find those used.

 

Cosina-Voigtländer also makes them.

 

The Leica ones have room to add the coding, and I think the latest CV ones also do. If the notches are already cut, so much the better.

 

Remember, there are three types of adapter (35-135/24, 28-90, 50-75). The coding and adapter must match to function with M8 and M9.

 

 

(You're probably already aware of all that; no offense intended. )

[epand56]

3) Has anybody tried the LTM to M adapters from Europe, sold on eBay, with grooves already milled?

 

Also the last Voigtlander LTM to M adapters feature a groove all around the mount that allow for a permanent coding. It works great.