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Forum: Pentax SLR Lens Discussion
04-03-2017, 03:44 AM
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Which is consistent with the commonly accepted explanation that the SDM motor has a mounting issue and can get into a binding state, the latter being able to kill it for good. There were good posts about what exactly is suboptimal with respect to the mounting of the SDM motor and why it is only logical that the design is prone to fail.
The "capacitor theory" has no merit at all, AFAIC.
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Forum: Pentax SLR Lens Discussion
06-22-2016, 01:53 AM
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How does the data look like?
Are there a lot of similar values?
Many lenses don't support readout of lens data but nevertheless answer what appears to be garbage data.
If you look at the data of a 50-135, for instance, there will be a lot of different values and some structure in the data. In comparison, the readout from a lens that does not properly support this functionality, looks "broken". I'm not sure whether I have observed changing data myself in the past, but I could imagine that unsupported readout functionality has such side-effects.
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Forum: Pentax SLR Lens Discussion
05-21-2016, 08:18 AM
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Forum: Pentax SLR Lens Discussion
05-21-2016, 08:14 AM
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A K-5 II can do it with the help of a MODSET file on the SD card.
I'd be surprised if it were different for a K-5 IIs.
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Forum: Pentax SLR Lens Discussion
05-03-2016, 10:17 PM
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FWIW, I have posted some educated guesses of how to potentially convert the 60-250/4 in a respective "DA* 60-250 focus issue" thread.
Triggered by the recent discovery of some lens incompatibilities with the K-1, I looked at some lens EEPROM files and curiosity got the better of me when I found a 60-250 lens eeprom online and was able to make some findings.
I'm sceptical that I found the golden pot and have no 60-250/4 of my own for experimentation. However, perhaps someone with the lens can take it further to a solution.
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Forum: Pentax SLR Lens Discussion
01-28-2016, 04:54 PM
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The changes made to the lens data correspond to toggling flags that tell the camera whether the lens is SDM-equipped or not.
The reason why there are multiple flags to change (instead of just one per lens) is because Pentax treats a zoom essentially like a collection of primes. AF micro-adjustment data, for instance, is kept multiple times, so that there can be a different adjustment value depending on the zoom setting.
The camera uses the zoom setting to index the lens data and then fetches the values required as if there had never been a need for indexing. Hence the replication of the SDM flags.
The upshot of all this is that the 60-250mm will require the same value flipping, but in a slightly different range of the lens data (it for sure supports more zoom settings).
Its been too long since I looked at this so I don't know anymore whether the flags are also repeated with respect to the focus distances the lens supports.
If you look for the respective Pentax patent that describes the lens data layout, you may be able to figure out which other values to change.
Alternatively, you could try to just continue the replacement pattern as long as it makes sense, i.e., as long as you still find the correct source value in a position one would expect if the respective section in the lens data continued.
Sorry that this isn't more concrete help but I'm way too busy right now to investigate this in more detail. Perhaps it is enough of a hint, though, to get you or someone else going.
P.S.: I had answered the same question before in this thread and back then provided more details and pointers (e.g. to the patent).
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Forum: Pentax SLR Lens Discussion
09-12-2015, 04:27 PM
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The data in this file is partially specific to your lens copy.
It shouldn't be used for any other copy or else the chances are high that AF inaccuries at various distances and focal lengths will be the result.
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Forum: Pentax SLR Lens Discussion
06-25-2015, 02:58 AM
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The method would surely work for the 60-250 as well, but will probably require an adjustment of the locations whose values are altered.
The lens EEPROM stores AF adjustment data organised according to focal lengths so by comparing the difference in locations between the 16-50 and 50-135 you may find out which locations to change in the 60-250. As a crude guess, I reckon that the 60-250 would require the change of about twice as many rows as the 50-135, starting with 0020 and 0023, jumping in 0040 steps (perhaps it isn't necessary modify more rows but only the resolution for capturing focal lengths becomes coarser).
N.B. testing that theory by only applying a partial modification may not be easy because the EEPROM data is not only organised by focal length, but also by subject distance. Some users reverse-engineered the layout (in German). It seems that the SDM information is repeated in every "cell" ("ZELLE" in the German post) of the EEPROM data. You may want to compare that with the respective layouts shown in a Pentax patent.
Disabling the SDM contacts does not work.
The camera talks to the lens through the "digital" pin on the mount and this is where it gets the information from that it should use the SDM alternative. You could disable the digital pin, but then you'd turn the lens into an "K" lens, i.e., not get any AF at all.
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Forum: Pentax SLR Lens Discussion
05-29-2015, 10:08 PM
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No, it appears to be common for the SDM motor to die or jam, but the screw drive paths usually continues to work. It seems you encountered a rarer issue.
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Forum: Pentax SLR Lens Discussion
05-29-2015, 03:00 PM
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Seems like the clutch on your lens is broken. No software patch is going to fix it.
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Forum: Pentax SLR Lens Discussion
02-15-2015, 05:21 PM
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That's not true.
The body only needs to be able to read and write the lens EEPROM.
A K100D can do it and even features an in-camera editor for the lens data. I would suggest, however, not using the latter before a backup has been made.
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Forum: Pentax SLR Lens Discussion
02-02-2015, 07:00 PM
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Nice find!
According to the statement of a German technician the lens data does not allow to account for focus shift (at least not in a very precise way, see below). There is only one AF adjustment value per focal length (there would have to be several, depending on the aperture, if focus shift were accounted for).
However, user matthis posted the following list of correction values (I've translated the German):
Using PhotoMe and checking the manufacturer section, you'll find the following lens code (LC) fields:
LC3: K-value data. Corresponds to the gear ratio of the AF gear.
LC4: aberration correction, near distance aberration correction data.
LC5: light color aberration correction data. Correction value for light colour / longitudinal CA
LC6: open aberration data. Correction value for wide open aperture / spherical aberration.
LC7: AF minimum actuation condition. Probably a threshold value indicating when AF accuracy cannot be improved anymore.
LC8 apparently indicates the focal length.
Fig.3B of the patent provides a format.
User Voko reverse-engineered the mapping of some of the above LC fields to the lens data layout plus the position of focal length / distance dependent data from analysing/comparing multiple lens data versions for one lens.
I haven't looked at it with a lot of detail, but it seems his analysis differs from the layout provided in Fig. 3B of the patent.
The easiest way to reverse engineer the position of the AF adjustment values would be to use a Sigma dock. One would simply have to change all the AF adjustment values available in a systematic manner and then check what data positions in the lens data they affect.
It would be very easy to write software similar to the software that comes with the Sigma dock in order to calibrate all AF adjustment values of a lens, with the main difference being that for non-Sigma lenses, one would have to read and write the lens data manually with a camera body that is capable of doing so.
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Forum: Pentax SLR Lens Discussion
01-16-2015, 07:02 AM
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Surely, you will find that extending sarcasm in general is not the most inviting approach for asking others to spend their leisure time to help you.
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Forum: Pentax SLR Lens Discussion
01-13-2015, 07:17 PM
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That was an incorrect assumption as the lens data contains AF adjustment information that is specific to each lens copy.
Using someone else's lens data will most likely mess up the AF accuracy of the lens with results depending on focal distance and the zoom setting.
Again, given the current policy regarding SDM, it was not possible for Ricoh/Pentax to support you with deactivating the SDM of your lens. No reason to complain.
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Forum: Pentax SLR Lens Discussion
01-13-2015, 02:24 PM
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Lens data is specific to each lens copy. It would normally not be a good idea to use someone else's lens data in one's own copy. It is likely that the lens will show FF/BF behaviour afterwards.
The correct approach is to modify one's own lens data by just changing the SDM flags in the data.
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Forum: Pentax SLR Lens Discussion
03-08-2014, 04:01 PM
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The K100D even has a built-in editor.
After saving the original lens data, you could edit the data by using the K100D. No need to use Notepad+ or similar.
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Forum: Pentax SLR Lens Discussion
03-08-2014, 02:32 PM
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Forum: Pentax SLR Lens Discussion
02-22-2014, 07:00 AM
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Forum: Pentax SLR Lens Discussion
02-16-2014, 04:09 PM
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How do you know which addresses in the lens data to change?
Have you compared two different copies of the same lens model?
Have you had success with fixing FF/BF this way?
The power-zoom/SDM contacts should not play any role regarding the lens data readout and writing. However, I do not have any inside knowledge.
Is it always the same addresses that change values from readout to readout?
If not, then perhaps the SDM contacts would be needed for additional power but I think that's unlikely.
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Forum: Pentax SLR Lens Discussion
02-16-2014, 11:45 AM
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Why do you want to modify the data for these lenses?
The only lenses that need to be targeted are SDM lenses whose SDM motor doesn't work anymore but also have screw drive AF as a fallback option.
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Forum: Pentax SLR Lens Discussion
07-30-2013, 10:48 PM
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I posted the instructions how to activate the K100D debug menu just recently and verified that I could see the required menu entries for loading/saving the lens EEPROM contents and even for editing the lens EEPROM contents directly.
I personally would first save the lens EEPROM (to have a backup) and then use the built in EEPROM contents editor to make the changes. See the the post of this thread where it says "Using the DSLR directly" for the change in line numbers when you go this route. You then don't have to worry about using a suitable editor on your computer or even downloading one just for this purpose.
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Forum: Pentax SLR Lens Discussion
07-28-2013, 08:27 PM
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Do you own a K100D?
In this case you can access the debug menu simply with button presses:- Power off.
- While pressing [AE-L] + [INFO], turn the camera on.
- Firmware version is displayed.
- Press [MENU] -> [MENU] -> [INFO] within 5 seconds.
You'll then see the debug menu.
You'll have to press [MENU] one more time to get to the screen that allows you to read/write the lens EEPROM.
EDIT: The K100D even has the lens EEPROM editor built in. :cool:
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Forum: Pentax SLR Lens Discussion
07-21-2013, 06:45 AM
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Have you tried tethering software?
I understand PKTether can put a connected camera into debug mode as well.
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Forum: Pentax SLR Lens Discussion
07-21-2013, 01:33 AM
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For instance, on different platforms line endings are represented differently.
A "line feed" (ASCII code 10) or a "carriage return" (ASCII code 13), or both can be used to represent the end of the line.
The camera could potentially be confused by the wrong kind of encoding.
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Forum: Pentax SLR Lens Discussion
07-18-2013, 10:56 PM
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Downgrading a firmware version is normally not possible.
An older version will be rejected by the camera.
The only way to revert to an older version is to fool the camera into believing that the older version is a new version. This can be done by patching the older version.
I know that there were such patched versions around for the K10D.
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