Originally posted by UncleVanya In the file I have there are three C0's outside of "column 3". Changing those did not improve things.
In column 03 of rows
0X20, 0X60, 0XA0, 0XE0 (where X ranges from 0..7)
did you find 32 "C0" and did you convert all of them to "80"?
I'd be curious to learn if you encountered any other value in the above specified positions.
You'll notice that there is an "E3" in the row above each "C0" in column 03.
Try changing all 32 occurrences of "E3" in column 03 to "A3".
This is suggestion #1.
My thinking is that bit #6 (with value 64) of certain values represents the SDM capability.
The values (like "C0") appear so often, because the EEPROM is indexed with focal length and subject distance. For all combinations of focal length and subject distance (given a certain resolution, e.g., 12mm for the focal length), there is a dedicated entry in the EEPROM.
Given the above, I found other candidates for changing values. All the below should always include the changing of all "C0" in column 03 to 80. Here are the further suggestions:
#2: All occurrences of "E3" in column 02 to "A3".
#3: All occurrences of "FB" in column 0F to "BB".
While I have learned a bit about the structure of the EEPROM data from some
detective work performed by someone else (in German) and also looked at the related
Pentax patent, I make no guarantees. Please attempt any experiment at your own peril. I guess the worst thing that could happen is that the SDM motor and the screw drive motor engage alternatively in quick succession (in terms of the logic they cannot engage at the same time), but it seems you have encountered that case already and it did not cause further harm. Still, I'm making only educated guesses with my suggestions. Things would be a lot easier if the findings of the above referenced detective work matched the format the patent describes, but that's unfortunately not quite the case.
I'd be interested in hearing from you, in case you want to try the above.
Would you be able to share your lens eeprom file?
If found one online and might learn more by looking at another one.
BTW, I don't own a 60-250/4 and most likely never will. I'm just curious and think there ought to be a solution. It is possible, though, that Pentax did something non-standard with the 60-250 and hard-coded its SDM capability into the firmware of respective SDM-capable bodies (relying on the standard approach for some cases and on hard-coding for others).