Wednesday, September 05, 2007

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.

13 Comments:

Anonymous said...

if you post another article on a lens you have never ever TOUCHED or even SEEN in real life do you think anyone will take you seriously again (if any !)

forget about Pentax or find a way to be able to TEST those lens yourself damit !

you're a very strange guy you know ?

Jaka said...

RiceHigh does it again ... I marvel your Pentax hatred against.

I'll tell you if my DA* 50-135mm f/2.8 has the above mentioned issue when I get it.

The only thing I can say against Pentax is that the production rate is so damn slow. Other than that it's a good bang for the buck.

RiceHigh said...

If each time I post a new article on some reported problems on particular Pentax gear, I need to own or test those gear in question first, than I think I would have collected many more Pentax items than those I have now! Maybe those suffered users can send me in their gear for my full testing? ;-D LOL!

Anonymous said...

Why? It certainly wouldn't make you happy. But any of the articles you post is, technically, hearsay...
http://en.wikipedia.org/wiki/Hearsay

RiceHigh said...

So, everything you read on the net is actually "hearsay". Why YOU bother?

Anonymous said...

Entertainment, which is a bit lacking here.
Some hearsay is a bit more relevent than others. Again not here.
Hearsay, rumor and unsubstantiated facts (95% (just a guess you see) of internet) can help one make a decision if each is weighted and verified by ones own research. Take the flash issue for an example. Grassroots pole on pentaxforums shows 90%(approx) of Pentax owners have no failures w/ their onboard flash. Reading rumors,posts, and hearsay would make me believe that the percentage would be MUCH higher. Now the pole itself is probably skewed so a thinking person would use both of these and decide for themselves what it is all worth but to assume any of this as gospel would be downright foolish. Trend does show a fairly good success rate (varies by model BTW)but also room for improvement (low single digits would be preferred).
Same w/ the 50-135. Tons of great photos, tons of working lenses. Some really bad duds. Critical problem? Probably not. Manufacturing defects rise as cost/profit margins get challenged. This is across the board and w/ all companies. Some are just a bit better than others. No order of magnatude different yet. Nikon had problems w/ the 200 originally. Canon w/ the MkIII ect. I'm not going to fall apart over the posts regarding these but would take 1 comment by a more reputable source (lum landscapes/photozone/dpreview) over a dozen lesser sources (unless credentials are known) and even these have a right to be questioned. Taking Klaus's rejection of the lenses due to centering defects without also adding his comment regarding ALL lenses (which I posted as a comment in another of your entries) is just sensational journalism, which you attempt to spin into some authoritive statement without much substance really. Not to mention your attempt at looking impartial, when in fact your not. Maybe I'm wrong but it seems quite obvious to me (and a host of other hearsayers :))

RiceHigh said...

> Anonymous said...
> Take the flash issue for an example. Grassroots pole on pentaxforums shows 90%(approx) of Pentax owners have no failures w/ their onboard flash. Reading rumors,posts, and hearsay would make me believe that the percentage would be MUCH higher.

Do you mean this?

So, the good ratio is 89.57% at the time I make this reply, out of a sample size of 125. That means that one Pentax DSLR user out of ten have had their built-in flash failed already for at least one time. Is that more than enough? I wonder why you are saying that this is an over-exaggerated issue?

Do note that according to your argument, the poll you are reading is also a "hearsay" and you could actually draw no conclusion based on it and that as you have also said, the sample size is really small, why (you still) bother?

Anonymous said...

So 125 sample size is too small to you? Well sure beats the pants off the one or 2 samples you base "your conclusions" on. How many samples do you need to draw a valid conclusion??? YOU only seem to need 1 or 2 (or maybe up to 5) before you make some broad accusations about your "findings". Do you see how silly you are?????
Again point is 1 out of 10 on a small sample is invalid. Apparently 2 people posting underexposure on the 18-50 was enough for you to condemn the lens as "worthless". ALL it takes for you is to find a few bad samples and you build your mountain out of a "possible" molehill.......
Still don't get it yet do you????

RiceHigh said...

> Anonymous said...
> So 125 sample size is too small to you?

According to your own silly argument, it is. Of course, the truth is it is NOT. Also, forget also about the poll is just a "hearsay"? Why YOU bother??

> Well sure beats the pants off the one or 2 samples you base "your conclusions" on.

You are wrong again. I have only ONE sample of each of my dozen of Pentax lenses. So, it is very obvious that my experience is INVALID and should be ignored! I do have owned/loaned/used 3 *ist D bodies, 3 *ist DS, only one K100D, 2 K10D bodies though. But according to your "logic", all these should be ignored just because of the "small" sample size I have touched on.

> How many samples do you need to draw a valid conclusion??? YOU only seem to need 1 or 2 (or maybe up to 5) before you make some broad accusations about your "findings".

I think only you can answer this silly question. I am not the QC department of Pentax, so my answer is that "I don't know". But if I follow you argument and "point", the answer is simply that NO ONE can draw up *any* conclusion, probably not even Pentax!

> Do you see how silly you are?????

Yes. I found myself to be utterly silly and non-sense to keep "communicating" with "talent" like your goodself. And I think this would be my last conversation with you, guy!

Anonymous said...

For all I know you never owned any Pentax stuff, just made it all up for your own amusement.
And yes I've always believed that everything you do should just be ignored (more correctly, just archived in with a pile of other trash, to be sifted through and then maybe some thread of truth can be gleaned)
RICEHIGH SAID
I think only you can answer this silly question. I am not the QC department of Pentax, so my answer is that "I don't know". But if I follow you argument and "point", the answer is simply that NO ONE can draw up *any* conclusion, probably not even Pentax!
NOTE: NO ONE can draw *any* conclusion....
YET
RICEHIGH SAID:
So, if one asks me if the DA* worth its price, in particular for the DA* 16-50, I would say "No" without second thought.
Anonomous says: You made a freaking conclusion based on one or 2 reports and at the same time ignored reports to the contrary (or at least some "observations") . Technically there were not enough posts to draw any real conclusion)
HOW can you honestly say "NO ONE can draw up *any* conclusion when you do that very thing in one way or another in almost EVERY blog post...

SloPhoto said...

I do not understand what the comment on flash is doing here, but it is not a QC issue across all of the cameras.

It was the first batch of cameras that had the problem, mine included.

Anonymous said...

Again, no facts just two users experience a problem. ANyone reading this blog should know ricehigh knows nothing of photography, never posts pictures and is just a general know-it-all. (But he really knows nothing). So read this blog and laugh at the person as he has no clue except to distort the truth in every entry he posts.

jaka said...

OK, I tested the 50-135mm f/2.8 yesterday when one of the local shops had a presentation of new pentax lenses and I must say I'm impressed. No focus issues, beautiful bokeh and very sharp in low light across the whole area - regardless of aperture and focal length.

Some of the quick test photos I took yesterday at the presentation (exif intact, shot in DNG, converted to JPG with Camera RAW 4.2):
Sample 1
Sample 2
Sample 3

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