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06-25-2016, 03:03 AM   #16
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QuoteOriginally posted by Ptitboul Quote
Part of the EXIF Pentax MakerNotes reflect the data exchanged between the body and the lens.

The first type of communication between Pentax lenses and bodies is electric, not electronic. These are the ones mentioned in bdimitrov's site Features and Operation of the Ka Mount
Then, electronic communication has been added.

The 16 bytes you are mentioning are probably the first version of electronic communication between Pentax bodies and lenses. These bytes are named LC0...LC15 in ExifTool source, the reference for these names being a set of patents.
The signification of some of these bytes is well known, but most of it is unknown.

I have contributed to the understanding of the LC2 byte. As you can see in the comments in the source of ExifTool, early Sigma lenses did not use an appropriate value for LC2 (they always reported a minimal focus distance of 0.50m), but recent Sigma lenses are OK.

I have tried to collect other LC values for various lenses. This work is not part of ExifTool because it is unfinished. Here are some findings:
Some LC values are constant for a given lens, some depend on the focal length for zooms, some depend on more parameters than only focal length. All zooms have 16 possible focal lengths, e.g. the DA* 60-250 focal lengths are 60, 67.5, 75, 80, 87.5, 97.5, 107.5, 117.5, 127.5, 140, 152.5, 170, 180, 200, 220, 250.
Most LC values can only take a few possible values. E.g. have have seen for LC15 only 0x03, 0x1b, 0x3b, 0xfb and 0xe3 (the last one for a DA 16-50 at 42.5mm, but I suspect an error in the transmission of the value by the lens, there seems to be no error correction in the transmission).
Thanks for the info. I find it very useful. ExifTool source gave me more ideas how to interpret the values.
Also I found some interesting threads in the ExifTool Forum.
I see that I have to play with more lenses and explore the values


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