[Ratmagiclady]

Here's where I get a litle grouchy: seems like if kids spent half the time learning to focus as they did complaining about AF systems they never even touched, there might be a lot more sharp pictures in the world.

[lol101]

Watch the videos in my sig. 17-70 SDM is as fast as 16-45. The only slow--in terms of hunting--SDM lenses are 50-135 and 55.

DA 40 f/2.8, albeit a fast AF-wise lens, becomes SLOW under low light, with the old AF system.

True, but that's thanks to the super short focus throw on the 17-70.

SDM isn't what it could (should?) have been if you look at every other maker that has introduced ultrasonic focusing motors (even Oly is way faster...).

My fastest AF lens on Pentax was probably the FA 135f2.8 and it had a rather long focus throw (min focus distance 0,7m), it was way faster than the DA* 50-135SDM at 135 and could be favorably compared to Canon ring USM in terms of speed when mounted on a K20 so algorithms are not the weakest link in that case: SDM is!

[Slugger]

Has there been a problem with Accuracy? I've always heard said on the forums and my experience is that the issue with SAFOX being slower than other camera's systems is out weighed by it getting a lot more in focus 'keepers' that other 'faster' systems?

Yes there has.
My K10D misses focus all the time. Maybe this is on par with some of the competitors models but that doesn't mean that you stay happy with your focusing. I watched a video comparing the K20D to the K-7 and clearly some inroads have been made.

[pederd]

In some cases.

Watch the 300 f/4 video. On a DS, the screw motor is MUCH slower vs SDM on K20D.

BTW, the videos in the playlist are not mine.

I was also talking about the lock-on time. It takes a longer while for DA 40 f/2.8 or any other lens to lock on under low light--without actually hunting.

The screw motor on DS is MUCH slower than the screw motor on K20D!

[asdf]

True, but that's thanks to the super short focus throw on the 17-70.

DA 16-45 performs the same.

SDM isn't what it could (should?) have been if you look at every other maker that has introduced ultrasonic focusing motors (even Oly is way faster...).

My fastest AF lens on Pentax was probably the FA 135f2.8 and it had a rather long focus throw (min focus distance 0,7m), it was way faster than the DA* 50-135SDM at 135 and could be favorably compared to Canon ring USM in terms of speed when mounted on a K20 so algorithms are not the weakest link in that case: SDM is!

My slowest focusing lens was DA 55-300. Should I conclude that the screw driven motor sucks? Again, DA* 50-135 is the slowest focusing SDM lens there is, probably slower than 55. Again, look at the video of 300 f/4: SDM on K20D blows away the screw driven motor on a DS.

The screw motor on DS is MUCH slower than the screw motor on K20D!

Yes, there are many variables here. And it would be nice if there was a DA* 50-135 II, with a faster motor, and so on and on...

[RMabo]

Problem with 50-135 is that SDM performance is limited due to the double AF mechanism system. The 17-70 SDM, with one AF system and not double, is faster. According to Pentax when the 17-70 was released, Pentax has ditched the idea of two AF systems in one lens. So coming lenses will be either SDM or screwdriven, not both.

The AF system in the camera has really improved, it is "thinking" faster. Coming SDM-only lenses will be able to take advantage of this better than older ones, which can be seen as "first generation SDM". Of "first generation SDM"-lenses, the 50-135 seems to do the poorest job. (it is not slow, just not as fast as the others).

It is likely that Pentax are working on updated versions of their current DA Star zooms, there has been indications before of a new version of the 16-50 being worked upon, but I have - unfortunately - nothing more firm or confirmed of this matter. We have to wait and see.

As for the AF motor, indicactions that I have is that it is the same motor as in the K20D so no change there. The change is in the AF processing.

[PentaxPoke]

Some of them. Not all SDM/HSM lenses are the same. Some are slow, some are fast, etc. 50-135 seems to be a popular lens and it's slow--hence, the general perception that SDM is slow.

I must admit my experince is only with the 16-50 and the 50-135. The 16-50 wasn't too bad, but the 50-135 is glacial. Your video does clearly show the SDM on the 300mm is faster than SD on the DS. I wonder how much faster SD is on the k20 than the DS.

[Jonson PL]

That's MightyMike on these forums, and he already posted similar findings here. We both tried out the K-7 for quite a while at the Pentax Booth at the Imaging Expo here in Toronto this weekend. A bunch of other forum members were there as well and I think we tried almost every lens they had, and compared against both the K-m and the K20D in focus tests. The K-7 could lock on the black-on-black painted beams against the dark exhibition hall ceiling under almost "no light" conditions which my K20D would just hunt forever on. So it is not just *faster* but can lock on things even the demo D300 on the other side of the expo hall (tethered to a table!) simply could not.

However, even with a lot less "hunting" in general, the Pentax SDM lenses weren't any faster on the K-7 (I tried my own 50-135 to be consistent). Compared to Canon L-series USM (a ring motor around the lens focus element), the Pentax SDM (a drive motor in line with the screw shaft) is almost glacial on heavy zooms, so the AF system still has to wait for the elements to moved into the right places. But put a screw-drive DA limited prime on there and *bang* the K-7 is focused almost instantly.

Not sure about the "accuracy" since the SD card doors were quite securely taped shut and the image would only pop up on the (gorgeous) 3" screen for a second... but I'll assume the same as my K20D, which is quite accurate with good glass.

Thanks for your info from the show

[vizjerei]

However, even with a lot less "hunting" in general, the Pentax SDM lenses weren't any faster on the K-7 (I tried my own 50-135 to be consistent). Compared to Canon L-series USM (a ring motor around the lens focus element), the Pentax SDM (a drive motor in line with the screw shaft) is almost glacial on heavy zooms, so the AF system still has to wait for the elements to moved into the right places. But put a screw-drive DA limited prime on there and *bang* the K-7 is focused almost instantly.

Not sure about the "accuracy" since the SD card doors were quite securely taped shut and the image would only pop up on the (gorgeous) 3" screen for a second... but I'll assume the same as my K20D, which is quite accurate with good glass.

To be honest, I was disappointed after I try my 50-135 on K-7 in the show, as I see kinda no speed difference than it on my K10D but then the speed with 77mm is just crazily fast.

I however can confirm on accuracy, I try focusing object under desk, dark roof, took the digital preview and zoom it up to 6x, and i can confirm the AF is accurate.

[heliphoto]

Please, Pentax, let us choose screw drive over SDM in firmware!

Thanks for the feedback!

I'll sign that petition for sure! I bet the 50-135 could be a snappy focuser If I could just use the screw drive. As it is, the much bigger Tamron 70-200 is way faster to focus.

[wolfier]

I'll sign that petition for sure! I bet the 50-135 could be a snappy focuser If I could just use the screw drive. As it is, the much bigger Tamron 70-200 is way faster to focus.

I totally support. Partly also because of reports of "broken" SDM mechanisms on some 50-135's.

It would be really nice if there is a memory of a few lenses whether they use screw drive or SDM. Doesn't need to be 20 lenses as I think there are only a handful of lenses with dual mechanism...

[pentaxmz]

Yes there has.
My K10D misses focus all the time. Maybe this is on par with some of the competitors models but that doesn't mean that you stay happy with your focusing. I watched a video comparing the K20D to the K-7 and clearly some inroads have been made.

Could you please post a link to this video.

Thanks

[jsherman999]

Here's where I get a litle grouchy: seems like if kids spent half the time learning to focus as they did complaining about AF systems they never even touched, there might be a lot more sharp pictures in the world.

That's how I spent my 2008.




(A 50 2.8 Macro)



.

[Jonson PL]

I'll hold out on any more SDM lens purchases, until generation II SDM (if it ever happens) Please, Pentax, let us choose screw drive over SDM in firmware!

Good point.
Besides we ought to get get ring-type motors instead.

That's how I spent my 2008.


(A 50 2.8 Macro)
.

Beautiful shot