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05-05-2008, 04:07 PM   #16
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QuoteOriginally posted by flyer Quote
Oh! yes they do. It doesn't change the accuracy of the system, BUT the speed is there.
Yours is the first report I've read to that effect.

Mind you, my only experience with an SDM lens was a very brief trial of the DA50-135 on a K10D at a local store, and it felt sluggish (but silent).

05-05-2008, 04:23 PM   #17
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Hi offertonhatter

It has been my experience that when the K10D is switched to continuous AF mode, the internal workings of the camera go into a kind of 'hyper-active' dithering mode. The electronics / optics seem to find great difficulty choosing precisely what to lock onto, whilst never entirely succeeding ! After much experimentation however, I've settled on using centre focus mode in conjunction with Single Auto Focus on the K10D and that seems to lead to far less 'hunting' where auto-focusing anomalies are concerned. Admittedly I don't specialise in taking action or sports photography, so AF problems have never really bothered me much in this respect. Thus far I only own two non-Pentax lenses (Tamron 18-250mm & Sigma 10-20m), but understand that AF accuracy is markedly improved when using the latest Pentax SDM lenses. Hope this info helps somewhat ?

Best regards
Richard

Last edited by Confused; 05-05-2008 at 05:13 PM.
05-05-2008, 04:35 PM   #18
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In reply to Steve's (stevebrot) comment:

QuoteQuote:
The continuous (AF) mode simply does not work for tracking moving objects.
If that's the case, it kinda begs the question why Pentax decided to incorporate continuous (AF) on their DSLR's in the first place ?

Best regards
Richard
05-05-2008, 04:49 PM   #19
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My experience with Pentax AF is it will eventually lock onto anything that is not moving. As soon as there is movement, the AF doesn't do so well anymore.
Having said that, it is as good as anything else out there in it's price class (cheap and cheerful). If you want really fast AF, invest in a high end Canon or Nikon. They are several levels above Pentax in this respect. Unfortunately, the compromise is that you have to use Canon or Nikon lenses, neither of which I like the overall image qualities of.

05-05-2008, 05:09 PM   #20
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Problem w/ the Pentax AF?, try this link, even a lowly K100 can do these amazing shots.

http://i214.photobucket.com/albums/cc306/mphmilkman/airshow%2008/IMGP0623.jpg

Cheers,

Rene
05-05-2008, 05:10 PM   #21
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Hi Wheatfield

A few years back I was on holiday and taking a ferry crossing between the Channel Islands and France, when I struck up a conversation with a guy toting a C***n 1DS Mk11 around his neck, which he loaned me for 10 minutes whilst he went to get some refreshments. Apart from the fact that this bulky leviathan weighed an absolute ton, I have to admit that the autofocus mechanism was absolutely instantaneous. Despite this however, I genuinely had not the slightest regret in handing the camera back to him a while later, although I paid him the usual polite compliments.....

Best regards
Richard
05-05-2008, 05:43 PM   #22
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QuoteOriginally posted by RBellavance Quote
Yours is the first report I've read to that effect.

Mind you, my only experience with an SDM lens was a very brief trial of the DA50-135 on a K10D at a local store, and it felt sluggish (but silent).
The difference with SDM lenses vs screw drive autofocus is night and day. You should try the 200-2.8: you'd be amazed at how fast it focuses. The zoom are a tad slower, but still faster than the screwdrive. I'd have a hard time going back to my old Sigma lenses with screwdrive.
05-05-2008, 06:27 PM   #23
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I find it inconsistant, which drives me mad as I'm aware of it's inconsistantancy and go out of my way to focus/recompose to try to ensure in focus pictures. It gets it right most of the time, but on those occasions it doesn't, it's very frustrating.

05-05-2008, 09:06 PM   #24
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QuoteOriginally posted by flyer Quote
Oh! yes they do. It doesn't change the accuracy of the system, BUT the speed is there.
I'm not sure I agree that it's faster. It seems faster because it's virtually silent, but I've had some screw drive lenses that focus just as fast.

However, on my K20D, the focus is just as quick as it ever was, with much less hunting, and very accurate.
05-05-2008, 09:13 PM   #25
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Here's my experience with AF-C on the K20D and the 50-135.

First one is low light, wide open, ISO 2000 with the 360 flash (need to tweak the colors, but that's not an AF problem):



Second one is in broad daylight with runners approaching me. AF tracked them all the way. In fact, out of ~100 shots that day, I only had two that misfocused.



Check the full size shots on my Flickr stream. They are perfectly focuses as far as I'm concerned.
05-06-2008, 04:32 AM   #26
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Frustrated about Frustrated

I am counting.

23 posts now about a subject where the OP has not yet posted a single example of his problem.

The discussion is all well and good, but Please, where's the proof.

If the purpose of this was to start a pentax bashing/defending thread about focus problems, you have succeeded.
05-06-2008, 04:41 AM   #27
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QuoteOriginally posted by offertonhatter Quote
Help on moving objects would be appreciated
My first question would be....

In what mode do you have the focus setting? Auto, select or Spot?

If you are using the 11 segment auto focus setting, your camera, even in "AF-C" may not look for the object on which you are trying to focus.

Anytime I use the AF-C setting on the camera, I use spot focusing and center weighted metering.

It might also help to turn of the "SR" if you are panning while using AF-C.

Not that you are, but I sometimes feel that a lot of folks are trying to allow the camera to do all of their thinking for them.

Hope that helped?

Ed
05-06-2008, 06:36 AM   #28
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QuoteOriginally posted by rfortson Quote
I'm not sure I agree that it's faster. It seems faster because it's virtually silent, but I've had some screw drive lenses that focus just as fast.

However, on my K20D, the focus is just as quick as it ever was, with much less hunting, and very accurate.
With a wide angle lens, the focus throw is shorter than a tele, so the difference doesn't show up as much, but with a telephoto, SDM lenses are faster by a good margin.
05-06-2008, 06:54 AM   #29
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QuoteOriginally posted by flyer Quote
With a wide angle lens, the focus throw is shorter than a tele, so the difference doesn't show up as much, but with a telephoto, SDM lenses are faster by a good margin.

Okay, I can buy that. I'm not really concerned with AF speed since it's always been fast enough for me. I haven't done any side by side tests.
05-06-2008, 07:01 AM   #30
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another thing about the SDM motors is that they can change direction MUCH quicker than screw drive. screwdrive has all the momentum of the glass PLUS gears, PLUS the motor, whereas SDM has the momentum of the glass and much different motors to counteract
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