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09-11-2007, 09:23 AM   #1
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Compare Canon and Pentax AF Performance For Action Sports

This topic has been discussed here before, but I continue to be frustrated by the inability of my system to auto-focus properly while trying to photograph my son's soccer games. These are daylight games played on a field that is about 80% of the size of a professional soccer field. The problem is that an unacceptable percentage of the shots are not in sharp focus when using AF.

I'm using a K10D body and the Sigma APO 100-300mm f4 EX DG lens, mounted on a monopod with SR off. Usually I use AV or TAV, and keep the aperture around f/5, shutter speed between 1/750 and 1/1250, and adjust the ISO accordingly.

The problem is that the subject isn't actually in focus when the shutter trips, even though the AF is locked on the proper subject. If the subject is moving towards or away from the camera, then often the camera focuses behind or in front of the subject. The camera simply doesn't adjust the focus fast enough to keep up with the quickly moving subject. It isn't a focus calibration problem, as the focus is perfect for stationary and slow moving subjects 99% of the time. It's just that the AF can't adjust fast enough if the subject is moving too fast.

I've tried all the AF options and permutations including allowing the camera to auto-select the AF sensor, keeping it on the central sensor, AF-C, AF-S, etc. AF-C just doesn't work well at all, with about 60% of the shots out-of-focus. AF-S with the central sensor gives the highest percentage of focused shots. I also use manual focus (pre-focus on where the action is going) but that is also a hit-or-miss proposition. I purchased the digital, auto-focus equipment for the purpose of using AF in this situation. What is frustrating is reading accounts from sports photographers using better equipment and having no problems with focus tracking. My Pentax system just fails miserably at this.

I am seriously considering investing in a different system with superior AF performance. From my research and my informal tests, it appears that Canon does the best in AF speed in bright conditions. I am considering a Canon 100-400 f4.5-5.6L lens with a suitable body, perhaps a 30D (on a close-out sale) or a 40D. I can't afford a Canon 1D. Does anyone have experience with both the Canon equipment and Pentax equipment, and can tell me if the "pro-sumer grade" Canon will be an improvement?

(Note: I like my Pentax system for other types of photography, and I have no interest in starting an argument of which is "better." I am asking if I can expect better AF performance from the Canon equipment in my particular application as compared to my Pentax system. I hope that someone has enough experience with both systems to offer an informed opinion.)

09-11-2007, 09:50 AM   #2
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K10D seems to have problems in this regard,...but it si confusing why AF-S be better than AF-C which is designed for this instance.

This may help you in trying to resolve this issue.....
tests of digital cameras (in french) - Pentax K10D focusing speed [Page 2]: Pentax SLR Talk Forum: Digital Photography Review

I don't even have my K10D in my hand yet,,,so no first hand suggestions. Good luck!
09-11-2007, 10:12 AM   #3
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If I were a sports shooter I would not use Pentax. Pentax's priority has always been their glass and unique body features, never AF speed. The odd thing is that Pentax invented auto-focus, among other things, but they allowed others to pass them by. It is their weak link. The other companies have their weak links too, so be carefull that you don't trade one problem for another equally exasperating one.
09-11-2007, 10:21 AM   #4
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I feel your pain

Gary,

As big a fanboy as I am for Pentax I don't think I would recommend their system for this type of shooting. Nor would I recommend any of the other systems unless you are willing to jump all the way up to the new Nikon D300. This is not an area I know a great deal about but my research seems to indicate there are two separate issues here. The first being technique. If you listen to a cranky old codger like jfdavis58 that frequents this forum on a regular basis I'm sure he would tell you something like shooting sports is hard to learn and he can do it with a spotmatic just as easily as he can with the latest greatest $10,000 Canon. There is a great deal of truth in that, it take a lot of practice.

However, for us non professionals that need as much help as we can get equipment does play a roll in our success or lack thereof. From the reading I've done it appears the Canons and Nikons are slightly better than the Pentax but I really have my doubts if there is that much difference in AF speed and accuracy unless you reach into the top end models. The Nikon D300 just might be a different animal. The specs indicate it will be capable of giving you what you want. IMO if I were you I'd keep on working on your skills until the D300 is available.

Regards,

Ken

09-11-2007, 10:29 AM   #5
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I also believe AF is a pentax weak link, that is, with the k10d the af is fine but the tracking/continuous AF is lacking. I dont know if canon or nikon is the best in this regards, it depends also on the body. I suspect the upcoming D300 from nikon, inheriting the 51 focus points from the D3 would have something to offer altho i guess that is out of your price range. But yes canon and nikon have better tracking af than pentax.

As for pentax i suspect the DA* SDM lenses, and for sports the upcoming 60-250 should be as good as u can get with zooms in terms of speed, but again the tracking performance prolly will not get that much better. I dont really expect pentax to release a speed-oriented new camera either, altho a possible future higher end pentax would prolly have improved AF to justify higher price over the k10d. but pentax just isnt the sports shooters best friend.
09-11-2007, 10:33 AM   #6
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How about the DA* 50-135 SDM? This should be better for this type of pictures..
09-11-2007, 10:59 AM   #7
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QuoteOriginally posted by davemdsn Quote
If I were a sports shooter I would not use Pentax...
I can't comment on sports such as soccer, football or other "humans moving around in unpredictable patterns sports" but for "vehicle sports" such as motorcycle racing or bicycle racing the K10D and even the K110D perform well, BUT, you have to use zone-pre-focusing. I do not rely on auto-focus for the reasons the OP brought up. The AF just will not keep up well. I focus on a point on the track where I know the vehicles will pass thru and press the shutter as they enter the zone of focus. This works for head-on shots as well as panning shots.

(I guess I am one of the old codgers... LOL)
09-11-2007, 11:30 AM   #8
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Ditto for pre-focusing in a zone. I had to do the same at the US Open (tennis). However, the issue was that I couldn't keep the focus point on the subject, so the K10D kept locking on the background when I missed. Canon and Nikon both have a dynamic focus point mode that tries to track the objects that are moving and will move the focus point for you. That's something I wish Pentax would look at, but I suspect they're too busy thinking "oh crap, Nikon and Canon have 50+ focus points...we're going to have to release our next version w/ 60+ focus points to beat them" :-)

09-11-2007, 11:40 AM   #9
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I have a K100D and haven't had any trouble with motorsports photography (other than my shaky panning at 1/160). I've found that using the center focus and Af.C modes provides the best results. I haven't had trouble with cars going 100+ mph. With all that, I'm not sure it completely carries over to soccer where the players are not traveling on predefined paths...
09-11-2007, 11:49 AM   #10
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I own both the K10D and a 20D. I don't shoot sports, but I am an avid birder, and love to get BIFs all the time. BIF = Bird in flight fyi.

I am no great fan of continuous auto focus on either camera. I much prefer single shot AF for birds and other fast moving critters. With the Canon, this works very well for the fastest subjects. On the Pentax, there is much hunting, and it isn't really fast enough to be terribly useful. Trap focusing works out well on the Pentax for birds, and have had to resort to this at times.

Now, the Pentax is fairly noticeable in how much slower its AF is compared to Canons. This is due to Canon's better AF technology, and also faster motored lenses. You can slow down Canon's AF system nicely by placing a non USM or HSM lens on their bodies. So AF is dependent upon both the camera body and the lens attached to it.

This is probably one of Canon's biggest advantages over Pentax right now.

Now, I can recall the day when auto focus was a dream. We all had to manually focus on our speedy subjects. We didn't get so many keepers, but it was more then sufficient. So a big thumbs up for technique. What worked then is still very applicable today.
09-11-2007, 01:25 PM   #11
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QuoteOriginally posted by Chako Quote
Now, I can recall the day when auto focus was a dream. We all had to manually focus on our speedy subjects. We didn't get so many keepers, but it was more then sufficient. So a big thumbs up for technique. What worked then is still very applicable today.
Thanks for all the responses. A few comments:

I didn't have an auto-focus camera until about February of 2006. I was content to manually focus my Pentax LX for the landscape, portrait and travel photography that I did. But as my son's soccer skills progressed, I tried some action shots and got some excellent results using the LX and my old M*300mm f/4 lens. The M*300 has about 270 degrees of focus travel, so you really have to pre-focus and select your spot. But I got a few beautiful slides from some games.

One reason I went to digital was to be able to easily share sports action and other family photos. After using the my first digital body with the M*300, I though that an auto-focus, long zoom lens might make things easier and give me more opportunities. I can (and still do) manually pre-focus and try to snap the picture at the precise moment when focus, composition and action come together, but reliable AF would certainly make things easier. I frequently use manual focus to get the focus exactly where I want it in portraits and similar shots. It is just a lot harder when your subject is running around in a somewhat unpredictable fashion!

I suppose I can live with the limitation of manual focus for sports action, but I've read countless magazine articles and sections of photography technique books in which the pros describe their success with auto-focus, and I'm beginning to feel left out of the games with my slow-focusing Pentax-Sigma rig. Of course, the pros are all using the high-end stuff. Unfortunately, I can't justify the cost of a Nikon D3 with a 200-400mm f4 lens or a Canon 1D Mk. III with a 300 or 400mm f2.8 L telephoto.

I have a DA* 50-135mm f2.8 SDM lens and I like it a lot. Unfortunately, 135mm is simply not enough reach for this size soccer field. I thought about bringing it to the next games simply to test focus speed when the kids get close. I have also considered the possibility of using a DA* 60-250mm when it is available, but 250mm is still a bit short and it will probably be a year before it is available. The DA* 300mm f4 also looks interesting and may be available sooner. I would lose the flexibility of a zoom, however. But there is still the question of whether it is simply the slow focusing lenses with the camera body motor, or a limitation of the Pentax AF technology. That is why I was hoping to find someone who could tell me whether a mid-level Canon body with a mid-level telephoto (e.g, the 100-400mm or a 70-200mm with a 1.4X converter) would make a big difference.

I don't consider sports photography to be my main interest and I do a lot of other things with the camera. But I am feeling a bit frustrated when so many shots appear out of focus, and I wanted to know if there was a better alternative at a price I could afford.
09-11-2007, 01:35 PM   #12
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hi, from memory there was a lot of talk about people having the heaps of focus problems (from memory excessive hunting bf/ff) with sigma 100-300 with the ist D and DS (before k100/k10) it might worth a search on dpreview to see if there was any great revelations (but you'll probably want to go back a fair bit in the search)
09-11-2007, 01:38 PM   #13
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What I'd do in your situation is just go out and rent a Canon setup. You can probably do it for about $150 and then you'll know exactly where they stand.

SLC
09-11-2007, 01:56 PM   #14
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That is a good idea. Rent or loan one from a friend to try it out.

I do know that my Canon is fairly accurate and speedy in focusing. I have noticed with Pentax that I am always astounded in how wishy washy it is. For some unknown reason, I have found the K10D tends to favour the center AF focus spot. So much so that I have seen myself try to focus on an offset object, but the camera will unintelligently go past the main subject and focus on the background because the center focus area is over that instead. The canon is fast and predictable. The Pentax still has me scratching my head in this regard. Not saying that Pentax cameras are junk. They just need to work more on their AF and how it works.
09-11-2007, 02:18 PM   #15
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ditto...renting a Canon setup would answer your question.
I remember someone in a Canon forum griping that their 1DmkIII could continuously autofocus on a baseball player running from home to 1st and he said all the pics were in focus w/ the 1DmkII. I posted it on DPR to see if any Pentax users have tried that and none have...

I suspect Canon has that "fire only when locked" feature that Canon/Nikon's AF-C systems have as an option...we only have the "fire when shutter is pressed" option...
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