"6 bit coding" Of what use?

I tried to download the .pdf from Leica but the download "stalled." Several times.

 

I also searched photo.net but didn't find an answer.

 

So, other than informing the M8 the identity of the lens attached, are there other functions of the "6 bit

coding?" Are there functions that I won't have if I use uncoded lenses?

 

Thanks.

<<Are there functions that I won't have if I use uncoded lenses?>>

 

You will be unable to pass water without severe pain.

 

Seriously, the manual for the M8 says, "This information is used among other things for

optimizing the image data. Thus vignetting which can be particularly noticeable with wide-

angle lenses and large apertures can be compensated in the respective image data...

 

...Flash exposure and flash reflector control also uses the lens data...

 

...in addition, the information delivered by this 6-bit coding is written to the respective

EXIF file for the picture..."

 

Hope that helps.

Thanks, Paul, for your rapid response.

 

So, does the 6-bit coding offer anything that can't still be done in digital post-processing?

I'm not sure it can, and it's far from clear that it's worth having one's non-coded lenses

altered, unless this matters:

 

The M8 requires the user to choose to enable the camera for 6-bit recognition via the

menu. This does not happen automatically upon fitting a 6-bit lens (I have the 28/2.8

ASPH).

 

Neither is 6-bit recognition automatically disabled upon changing to a 'normal' lens.

 

The manual instructs users to turn off the recognition function when not using a coded

lens 'to prevent malfunctions'. I had switched from coded to non-coded freely without

disbaling the function before I read this, and nothing fried or exploded.

 

Perhaps there is some technical reason why it is not possible to have it so the camera

recognises whether it is a coded lens or not and disables/enables the function accordingly.

I suppose it's a bit of a nuisance that it can't.

Sorry, that should have begun with 'Not sure it does...'

From M. Reichmann's review on LL...

 

6 Bit Lens Encoding

Since earlier this year Leica has been encoding new M lenses with a 6 bit data bar on the

inside of the lens mount that can be read by the M8 and subsequent cameras. This tells

the camera the focal length, maximum aperture and other information about the lens. This

information is used by the camera to pre-condition the raw file so the raw converters can

accomodate vignetting correction and provide EXIF information. Older M series lenses can

be updated at a modest cost by Leica service centers.

Leica is offering a rebate when you buy a new lens. Leica will encode two of your legacy lens

free. Check with Adorama.com by looking up their Leica lens.

How does the camera know if I am at 28mm or 50mm on the Tri-Elmar? The only linkage is

to the frame selector. I am just skeptical.

My understanding is if any anti-vignetting is applied to the image, of course it will only be to the jpegs. So if you shoot RAW, there is no reasong for the 6-bitting of older lenses (unless you want that little tag in the EXIF data, I suppose...).

There are conflicting reports on the coding. I've read (unless I completely misunderstood, which is altogether possible given my knowledge of digital workings is incomplete)some reports that it does apply some processing to the DNG, or maybe it's in the form of data that accesses a custom profile in the conversion software...again, not sure what I read. But I also read reports from a couple of real-world photogs that they tried a bevvy of non-coded lenses on an M8 and didn't find any more vignetting or chromatic aberration than those same lenses gave them on film. It would seem that the crop factor would mitigate some of the lens-inherent vignetting.

<i>pre-condition the raw file so the raw converters can accomodate vignetting correction </i><p>

Pre-conditioning implies that the image is modified in the camera's firmware, and that rather negates the purpose of DNG (raw).<p>

The data is written to the EXIF data, and useful to Capture One LE... if there are conversion routines that use the data.

Perhaps it is the Luddite in me but I just don't have any problems with corner fall-off (often erroneously called vignetting). Particularly with slides it puts the emphasis on the subject, not the peripheral matter. If the corner information is important then re-composition to is isn order. I am aware that the flames will come out for this heresy but combatting the effect involves a lot of expensive lens design. It was never a significant issue until the onset of the WA mania!

<i>If the corner information is important then re-composition to is isn order.</i>

<p>

Says you. The rest of the world isn't necessarily interested in conforming to your theories of composition.

I sent my current 50 Summicron to Leica New Jersey for the matte-black painting of internal surfaces mentioned in <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00IEQ5&tag=">this thread</a>. The tech I spoke with told me that lenses sent in for 6-bit coding are also being given this reflection-damping paint job at the same time. It was unclear whether he meant just 50 Summicrons, or all lenses generally.

If you have a lens that causes fall off in the corners and it isn't caused by a filter or shade; and you can't afford to get a different one, the only choice you have is to find some way of living with the results; and recomposition is the most logical expedient. I don't expect the rest of the world to conform to my notions of composition, but I do expect the rest of the denizens of this forum to respect my right to state my opinion. I have no problem with anyone who disagrees with the notions I might propound and expect them to express their disagreement if so motivated.