Wednesday, March 12, 2008

Improved AF Accuracy of the K20D (Under White Lights Only)

An experienced Pentax DSLR user, who has a bundle of Pentax AF/digital lenses and various Pentax DSLR bodies including the K100D, K10D and the new K20D, has tested and compared (side by side) the AF accuracy between his K10D and K20D with different higher grade Pentax fine lenses of his putting on both bodies:-

http://forums.dpreview.com/forums/readflat.asp?forum=1036&thread=27049158

First of all, here is his detailed comparison tests (two sets - will explain more below) regarding the AF accuracy differences with the DA 21 Limited lens on K10D against the K20D, pair of comparison test shots are posted:-

http://forums.dpreview.com/forums/read.asp?forum=1036&message=27066095

Do note that since the DA 21 was found to have strange focusing behaviour on the K10D that the focusing accuracy actually depends on the Av number selected (as well as if the lens is turned from the infinity or closest), which I have reported here before, the user also carried out a second batch of the test in the above to compare the focus accuracy of the K10D against the K20D under the procedure which he believed his K10D should work best.

Well, as it is mentioned in the user's opening post and can be seen from the above detailed tests and measurements, there are significant focusing errors with the K10D whereas with the K20D could do very well with the same DA 21 (and other various Pentax AF lenses he has as well, as told - so far he has not posted all the test photos with all different lenses in the thread, though).

Indeed, I was a bit susceptible on his report when I first read his opening post just because usually people would have some kind of honey moon period effect when they've received their new toys and usually think that the new toys are better (maybe just because they've got excited or actually time will tell for many things, when they use their "new" gear longer). However, since there is some solid measurbation evidence shown above, I think I should believe.

In fact, I am really glad and pleased that Pentax have improved their design finally (as it seems to be from judging from the above) after years of the same persistent AF problem for inaccuracy, at last. I do think that "late is just better than none"!

Well, I do believe that it is always a good thing to let Pentax and the public know about those annoying gear problems as wide as possible so that Pentax should listen and potential buyers/users should be fully aware of such problems as well, before they are sold. Furthermore, for letting more people to know about the problems, more pressure would be made to Pentax so that they are forced to improve to a certain extent, instead of letting the problems drag on for long or even forever! That's is in fact my clear objective in setting up and updating my this blog.

Now, have all the AF accuracy problems (just say for shooting static objects only) been resolved totally? So, what are some of the well-known problems? Just read back my early Blog article about the "AF Accuracy's Dependency on Lenses and Yellow Light", then you will know more about these.

On the other hand, here comes the bad thing as reported also by the above Pentax user who carried out also the test to verify if AF accuracy has been improved under the yellow lights, i.e., tungsten light source or any artificial light source with low colour temperature. Unfortunately, he found that obvious Front Focusing *still* occured, as always for ALL Pentax DSLRs:-

http://forums.dpreview.com/forums/read.asp?forum=1036&message=27066212

This is yet a disappointment, although I would not be of big surprise. In contrast, I have been surprised this time for what it has been proved that one of the most annoying "Pentax's" problems has actually been removed, with the K20D.

Since I shoot a lot under tungsten lightings which are often dimmer conditions, I had found that such AF system problems to be a big annoyance. This is in fact one of the main reasons that I was forced to get a Canon 5D kit in June last year. Later on, I got also the Canon 50/1.8 fast prime which I have never seen the Yellow Light Symptom of the Pentax DSLRs (which I was the very first person on the Net to conduct a quick experiment to verify this problem), even at fully wide opened and under very dim conditions and even with low contrast objects. More importantly, the focusing was still fast and decisive with the 5D at lower light conditions, unlike all other Pentax DSLRs that would hunt seriously in the same conditions. Moreover, do note that Pentax film AFSLRs like the expensive MZ-S flagship and the entry level model MZ-30 which I have both do not slow down like what the Pentax DSLRs would do under lower light conditions, neither. Nevertheless, the MZ cameras do shift a little bit with slight front focusing under tungsten lightings but the magnitude is not that large as those Pentax DSLRs - that I can tell - just believe it or not!

A few days before, I tried two units of the K20D, I am not overall impressed with the AF responsiveness of the K20D neither. That says the K20D required to think longer than I would expect for the AF motor start to move and it also need longer time to re-confirm the focus and re-adjust the lens as well. This slow responsiveness that I can feel easily is not really a good thing, IMHO.

Last but not least, here are the remaining posted test results (a few pairs of shots only) for the AF accuracy comparison between the K10D and the K20D with a few other different lenses which the above mentioned user has, which proves again the AF accuracy of the K20D has improved whereas the AF accuracy of the K10D is just rather poor:-

http://forums.dpreview.com/forums/read.asp?forum=1036&message=27066277

So, for those old Pentax DSLR users who have being wanted to upgrade just because of the particular deficiencies they don't like and ask me if it worths the upgrade to the K20D by now. My answer would be "Nope" at the current stage, undoubtedly. It is just because I won't spend another (US)$1,400 to cure only one of the long lasting and well known problems which exist mainly in all the previous models of Pentax DSLRs. Unless later on it can be confirmed that more of the old typical Pentax problems for the camera performance and accuracy aspects are cleared (like this time for the AF errors with different lenses), it is just too risky to put the bet *now*, I would say. Note that for $1,400, actually we could already invest into a few good lenses in the basic focal range for another better system, even if we are to start from scratch, like what I did last year (although these glass may not be as good as some of the original Pentax glass! ;-))

10 Comments:

Eric said...

You rag on Pentax for increasing their focus accuracy and then comment on how you have a 5D with an EF 50 f1.8, which is known to have focus accuracy problems. Combining the inaccurate EF 50 f1.8 on a full frame leads to even smaller, less accurate focal plane. No wonder we never see pictures from you. They're never in focus!!!

Jaka said...

You make me laugh RiceHigh. ... you were FORCED to buy a Canon 5D ... LOL

And you're comparing a camera that's aimed at an advanced enthusiast with a camera that's built for professional photographers.
I think there's no need to mention the price difference between these two cameras, or should I.

I agree that the K10D and the K20D could be better, but for this price they're great cameras (the K20D is a bit pricey but so was the K10D at first).

Anonymous said...

jaka, while the 5D was released as a semi-pro model, its AF system definitely lags behind all of today's midrange DSLRs except Pentax's. Its price has nothing to do with its AF performance but its large FF sensor. Even the 40D outperforms the 5D in AF.

As a matter of fact, right now there is only one company that did not fully update the AF system in its prosumer DSLR, and the company was behind in that area to start with. Can you guess which one it is?

Anonymous said...

And the K10D was not expensive. It was $899 body only when it was released in North America. The K20D is $1,299. That's almost a 50% increase in price. Has Pentax done enough to justify that? It's still a plastic body and the LCD is not high-res like the Sony A700's, which you could buy cheaper than the K20D now. The viewfinder is not 100%. The AF module is still the Savox VIII. Almost everyone else was working to improve in those areas, why didn't Pentax?

Some people talk about how nice its resolution is and thus how wonderful the K20D is as a landscape camera. However I'd bet that the $799 14MP Sony A350 will mostly likely match the K20D resolution in RAW. But you wouldn't see too many Sony users defending the A350 by saying how nice of a landscape camera it is.

Let's face it. The K20D is overpriced and there was not enough improvement over the K10D considering the price difference. I criticize Pentax's decision with the K20D because I have personal attachment with the brand and hope they release a camera that's more competitive and capable of increasing the user base. No matter what the Pentax fanboys say, it's doubtful the K20D/K200D will take users away from bigger competitors nor will they attract much of the new DSLR buyers.

RiceHigh said...

> Jaka said...
> You make me laugh RiceHigh. ... you were FORCED to buy a Canon 5D ... LOL

It's TRUE but actually nothing funny at all. It was a serious decision made upon total desperation.

> And you're comparing a camera that's aimed at an advanced enthusiast with a camera that's built for professional photographers.

So, what is/was the "advanced enthusiast camera" in the Pentaxland??

> I think there's no need to mention the price difference between these two cameras, or should I.

Price is not the only concern of mine, so do many old Pentax users as well, provided that the money we spent are justified, I do believe.

RiceHigh said...

> Eric said...
> You rag on Pentax for increasing their focus accuracy and then comment on how you have a 5D with an EF 50 f1.8, which is known to have focus accuracy problems. Combining the inaccurate EF 50 f1.8 on a full frame leads to even smaller, less accurate focal plane. No wonder we never see pictures from you. They're never in focus!!!

So, you should look at this before you made such a non-sense:-

http://forums.dpreview.com/forums/read.asp?forum=1032&message=24038144

Jaka said...

Where I live the K10D was 900€ (that's around 1,400 USD)when it came out and that is quite expensive by my standards. As I said before, the K20D in my eyes is not worth the money because of the same reasons you mention (old focus system, old light metering and old slow buffer for continuous shooting). The new sensor alone isn't worth the money if you ask me (Live view isn't even worth mentioning).
And again (I've said this before in another comment here on this page), I'm not saying that the K10D and K20D are bad cameras, I enjoy my K10D very much but the K20D just doesn't give enough bang for the buck. I'm waiting for next year's Pentax products that will hopefully bring something new and improved to the whole system.
After 20k+ shots my K10D still works great and the problems you've mentioned here are not showing (guess I'm not that much into pixel peeping). Light metering is something you have to adapt for every lens (for example, the 12-24mm f/4 overexposes, the 50-135mm f/2.8 exposes just right and the Sigma 17-70mm f/2.8-4.5 underexposes). Shooting basketball games hasn't been a problem for me (except for ISO800+ noise), focus works OK, sometimes misses but that's mainly my fault (can't compare it to a 1D with a 70-200mm f/2.8 tho). All in all, the K10D will do for another year, then we'll see.

eric said...

RiceHigh,
The nonsense is actually coming from you. You try to counter my statement by linking me to some test pictures that you took. How am I supposed to know you didn't adjust the focus after the fact? Once again, you can take all the test pictures you want but it doesn't prove a thing because your biased opinions remove any credibility to anything you do.

lol said...

I have seen absolutely no evidence of any back or front focus with any of my lenses under tungsten light with either the K10 or K20.

I had some with my Ds though.

aLL iN said...

was taking pictures at my friend's wedding this past weekend and was very annoyed at discovering the truly terrible front focusing problem i encountered with my k10d/tamron 28-75/2.8. shooting in daylight seemed to be fine, but attempting to shoot with spot autofocus and lowlight with a large aperture resulted in very noticeable front-focusing. i previously shot with a ds with this lens and did not see the same problem. i love my k10d when i have plenty of natural light, but AF under lowlight is simply abysmal.

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