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04-12-2014, 08:06 AM   #1
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Fast focusing lenses for K3

A recurring criticism I have noticed in various reviews of the K3 is that while Pentax/Ricoh have apparently greatly improved the autofocus system from K5** to K3, the current line-up of Pentax lenses
are not fast-focusing enough to take advantage.

How do (reputedly) faster-focusing lenses from Sigma (e.g., the 70-200 f/2.8 hsm) fair on the K3, if anyone happens to know?

Thanks!

04-12-2014, 08:15 AM   #2
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Something I would definitely like to try with the 120-300 if they ever release it for Pentax.
04-12-2014, 08:23 AM   #3
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On the K-3 they do very well - I have both the 70-200 OS and Bigma OS and they are both quick.
All screw drive lenses are fast too.
The ones that are slow are the SDM lenses.

I don't shoot Canon or Nikon so have no point of reference.
04-12-2014, 08:29 AM   #4
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In the DPR (gold medal) review of the K3 the main problem that they point to is with AF-C on subjects moving towards or away from the camera... Any experience with these scenarios and the fast Sigma lenses?

Thanks!

04-12-2014, 08:51 AM   #5
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The AFC tests I have done is with dancers so they are typically moving side to side more than front to back.
I haven't done track and field or bike races to test more rigorously.
04-12-2014, 09:25 AM   #6
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QuoteOriginally posted by crewl1 Quote
I haven't done track and field or bike races to test more rigorously.
I would view bike races as the ultimate challenge since the action is fast and potential targets are many and scattered over significant depth.


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04-12-2014, 10:12 AM   #7
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QuoteOriginally posted by yorik Quote
the main problem that they point to is with AF-C on subjects moving towards or away from the camera... Any experience with these scenarios and the fast Sigma lenses?
K-3 with the Sigma 70-200 HSM II does very well using AF.C on targets moving towards you. Better than the K-5, in my experience.

Some simple, perhaps not ideal, examples.


Birds on Flickr.

Focus maintained on rider:


Opening rider on Flickr.

Focus maintained on rider as bull charged forwards along the barrier and then pulled sideways away from the barrier:


Yellow chaps 1 on Flickr.


Yellow chaps 5 on Flickr.

Unfortunately action shooting is never just point-and-shoot though. Even D4 and 1Dx sports shooters will miss focus sometimes.
04-12-2014, 10:18 AM   #8
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Thanks to all for the (helpful and informative) answers!

04-12-2014, 11:39 AM   #9
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I do shoot runners. I also shot dancers one time with crewl1, using both his and my equipment. While shooting runners coming toward me is a challenge for the AF system, I found the AF performance was substantially similar shooting dancers indoors in lower light. So we should not discount the importance of AF performance in those scenarios.

I'm sure DPR tried hard on those tests, but it think they missed the boat. Pentax screw drive lenses do the best. The DA*300 comes close to them (but noticeably not as good - it not only seemed slower, but I completely lost focus more often with it than the F*300). No other Pentax SDM lens is even worth considering for fast action. The Sigma 70-200/2.8 OS HSM seemed to do better than the DA*300, and may have even matched the screw drive Pentax primes I use (FA*85, FA135, F*300). I've read the screw drive Tamron 70-200/2.8 now matches the Sigma on the K-3, and it should also come close to it on the K-5 II or IIs (but not the K-5 or older bodies).

The Tamron 17-50 and 28-75 f/2.8 zooms are the best candidates in the shorter range. Pentax primes work here too. But shooting runners coming at you on the FA43 is futile if you want to fill the frame with them, because they're so close by then that you can never get focus before they pass you. So any lens at these focal lengths must be taken with the forward motion mostly stopped - or else be a rather wide group shot.
04-12-2014, 12:01 PM   #10
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Good to know - thanks! It seems that my F 135 might be a good candidate for fast continuous focusing on the K3...
04-12-2014, 12:21 PM   #11
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QuoteOriginally posted by yorik Quote
Good to know - thanks! It seems that my F 135 might be a good candidate for fast continuous focusing on the K3...
Absolutely! You've got one of the best already!

Also, try out the FA77, and please let us know how it fares. I haven't had mine in a while, and I can't seem to get good reports on how well it works for action. In theory it will be good, but I'd really like to hear something definite.



Those focal lengths both work well for various types of action shots. The K-5 with the F135 is already good; the K-3 (or even K-5 IIs) will only improve its AF performance.
04-12-2014, 12:59 PM   #12
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The DA70/2.4 is also blazing. My Sigma 70-200/2.8 HSM II have never been a limiting factor for AF on my K-5, the OS version is supposed to be even quicker.
04-12-2014, 01:02 PM   #13
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QuoteOriginally posted by yorik Quote
A recurring criticism I have noticed in various reviews of the K3 is that while Pentax/Ricoh have apparently greatly improved the autofocus system from K5** to K3, the current line-up of Pentax lenses
are not fast-focusing enough to take advantage.

How do (reputedly) faster-focusing lenses from Sigma (e.g., the 70-200 f/2.8 hsm) fair on the K3, if anyone happens to know?

Thanks!
For lenses with built-in motor, the AF speed on the K-3 will be about the same as on other cameras, since the camera has no control over the motor. However, screwdrive lenses are considerably faster. Any DA or FA limited (except for the macro) focuses almost instantly

Fast-focusing SDM lenses that I've tested include the Sigma 17-70mm F2.8-4 "C", Sigma 35mm F1.4 "A", Sigma 70-200mm F2.8 and Pentax 18-135mm F3.5-5.6.

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04-12-2014, 01:25 PM   #14
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So I seem to have heard (in the above thread) , the Tamron 70-200 with screw drive is now as fast as the Sigma 70-200 HSM? That is awesome news, because just from my own research it seemed that the Tamron was the better lens, but on a k-5, slower focusing, and it's cheaper. If on a K-3 it's as ,fast as the Sigma, that would make it a steal.

I can pick up a Tamron for $649 new... a fraction of the cost of the Sigma.
http://www.ebay.com/itm/NEW-TAMRON-SP-AF-70-200mm-F-2-8-Di-MACRO-LENS-f-PENT...item486498f35c
04-12-2014, 02:47 PM   #15
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QuoteOriginally posted by normhead Quote
So I seem to have heard (in the above thread) , the Tamron 70-200 with screw drive is now as fast as the Sigma 70-200 HSM? That is awesome news, because just from my own research it seemed that the Tamron was the better lens, but on a k-5, slower focusing, and it's cheaper. If on a K-3 it's as ,fast as the Sigma, that would make it a steal.
Another Pentaxian in an earlier thread said that in a direct comparison on the K-3 it was only a tiny bit slower - not enough to matter. And I'd already read other reports that the Tamron AF speed is great now on the K-3, although they hadn't compared it to the Sigma.


My guess is that it's so close that a person's unintentional bias (according to whether or not they're used to hearing the screw drive) could come into play. So I'd say it's easily the better value, and I'd prefer it optically over the Sigma as well.
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