SDM = More AF Errors?

Recently, some different Pentax users, who had got the new DA Star lenses for their K10D, have reported that they found that more AF errors were resulted when the SDM lenses were used on their K10D, i.e., by enabling the SDM function to do AF ultrasonically. Just see the following hot thread:-

http://forums.dpreview.com/forums/read.asp?forum=1036&message=24652706

As we can see, the logic of the thread open person is simple and clear. If his DA Star lens is used on a non-SDM body with traditional body driven AF, the AF accuracy is good enough at f/2.8 wide opened. And then if another older generation non-SDM prime lens is used on his K10D, the AF is still okay for the same aperture and focal as compared. So, out-focusing only occurred when the SDM lens is used on a SDM body and thus he has drawn up the conclusion that the culprit is the new SDM focusing function, which should be in fault or having some bugs (hardware and/or software wise).

Do note that the Pentax Star lens are with hybrid AF facilities so that it can be used on both latest SDM-enabled Pentax DSLR or older body driven Pentax AF bodies, which is really a good thing as full backward compatibility is ensured. However, if the SDM would actually introduce more AF errors, then this will be a big problem and issue. In fact, this issue (if really existent) must be looked into seriously and tackled by Pentax in a very urgent way and manner. In the meantime, a custom function for letting the user to choose between SDM or body AF motor would be a viable interim solution that can be provided by Pentax quickly and easily, as only a new firmware update with minimal software modification is needed. Until some days later an ultimate technical solution arrives, this firmware option could be the true saver for users who have encountered the problem - and for the rest who do not find any problem, they can leave the setting at default and continue to use the SDM.

Anyway, to learn more about the reported cases and to judge if the problem is really existent, I think the lengthy thread cited above already provides quite some useful information for reference with useful sample photos posted as well. Nonetheless, as there are numerous numbers of opposite arguments followed down the thread (as usual and it is quite normal), I think any reader without a stance can think and judge the case in a more objective way, as far as possible. Of course, in the end, everything can still be concluded with the "bad sample" theory that the reporting users are just being the most unlucky ones. Or, again, simply the old but golden defensing rule of "user errors" can be applied. But, if you're about decided to buy the new DA* lens(es), will you take the risk? Will you bet, or not? (. . until some days the case has been made clearer.)

Update (Sept. 7): I have just a thought which've come over my mind. I think instead of waiting Pentax to confirm and hoping for a solution from them, why not be proactive and try to test the gear oneself and even to find out a possible solution that is actually ready available?

In fact, according to the past track record, Pentax have never admitted those more critical reported gear problems openly or they simply just not even responded publicly to those, even if for the problems that had been widely reported and recognised (clearly for their existence). As such, I think my last imagination or suggestion on the "interim solution" maybe just something not very realistic afterall.

So, what's my thought then? Still remember the old K10D firmware versions of Pentax which do not support the SDM? As such, with those older firmwares, it is most likely that the K10D will do AF *traditionally*, i.e., with the body AF motor to drive the Star zooms to do the AF. I haven't tried that myself though but I think it is most *likely* and it should work.

So, how to get back to the older firmware? Just see my next short article on that.

Update (Sept. 9): PentaxForums.com member SloPhoto has confirmed that older K10D firmware version 1.2, i.e., very probably for all firmware versions prior to the version 1.3, "will focus the DA* lenses using a conventional screw drive". So, this would be really a good news for all those users who have found problems associated with the SDM for their new DA* lenses on their K10D. At least now there is a readily available possible solution for them to try.