Questions on 6-bit coding

[alandash]

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I'm an old Leicaman that used screwmount Leicas and M3/M4. After some years of hibernating, I woke up to the call of digital M Leicas, and sold my wife and kids to buy an M9-P. I quickly found out that certain lenses I have are "verboten", such as the dual-range 50mm Summicron, the collapsed 90mm Elmar, etc. I purchased the M9P 2 weeks before the price dropped due to the new M announcements, and had to spend another $1,500 to buy another 50mm Summicron (used, 1994+ model). (I never did find the wind lever, frame counter, and the rewind crank on that M9P!)

 

I had a 35mm Summicron that DAG did a CLA on, and he also did a 6-bit encoding. The question now is which other lenses to 6-bit index? Some people said not to bother indexing any lenses that are 50mm or longer focal lengths. Is that true? I also have the 90mm fixed Elmar, 90mm Summicron, and 135mm Elmar.

 

I still do not understand what the camera actually does in response to reading the information of the 6-bit code. As a retired computer programmer, I am familiar with binary, octal, and hexadecimal notation, but only as it applies to software procedures.

 

Lenses are hardware, so presently cannot be physically altered by in-camera coding. My guess is that the image formed by the lens is post-processed in the camera, in the same way a person alters an image later on using Photoshop.

 

If new lenses become "smarter", perhaps they wiil use a motorized way of changing focus and entrance angles of tilt, hood movement, and aperture, etc., according to some coding.

 

Can someone clarify my confusion on the above?

 

Alan Dash

[jaapv]

That is right. The camera firmware,on reading the code, applies lens-specific corrections to the image file, mostly regarding vignetting and colour shift to the edges. Obviously that has far more significance for wideangle lenses than for longer ones. The lens design has to do with this as well. In addition the lens type information is written to the EXIF.

[efreed2754]

Hi Alan. Just curious to whom and how much you received for family. No names mind you....

 

To further Jaap's comments about the Exif file-- you probably have seen the M9 allows you to manually enter a lens each time it is attached and voila it appears when processing in your PC. Some, like me, usually forget to enter the code, rush of the moment or other elderly diversions I suppose.

 

So, no you don't need to 6 bit code, but many like not having to think about it and then see which lens was used.

 

Oh, not sure if the camera adjusts for raw files or just jpegs. Jaap's or someone else?

[01af]

Oh, not sure if the camera adjusts for raw files or just JPEGS.

Both raw and JPEG files get corrected for vignetting and colour shifts. The vignetting usually will be reduced, not entirely eliminated. There is no in-camera correction for distortion or chromatic aberration.

 

By the way, contrary to popular belief there are corrections for all recognised lenses, not just the wide-angles. However it does not matter whether the camera recognises the lens via 6-bit code on the bayonet flange or via manual selection from the menu.

[jaapv]

It is indeed true that all lenses get corrected. For most modern longer lenses, however, the corrections are so minimal to be barely visible in actual photographs- if at all.

[luigi bertolotti]

 

.........

If new lenses become "smarter", perhaps they wiil use a motorized way of changing focus and entrance angles of tilt, hood movement, and aperture, etc., according to some coding.........

 

 

Alan Dash

 

Hi Alan,

There are many speculations on the above topic... (if you surf our forum, will find a lot) : but the present 6 bit coding system is strictly limited to basic infos on the lens mounted, and it's a "one-way" system : the electronics into the body READS the bits through sensors... there is no way to TRANSMIT signals FROM the body to whatever is mounted on the flange, be it a lens or another device like an adapter, a bellows or so...

 

So if one day Leica will afford the task to make motorized M mount lenses (typically, to achieve an Autofocus system) they surely implement another technology to link electronically body with lenses.