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03-29-2012, 03:34 AM   #16
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A big thanks for all the great replies. Have previously been lead to believe that 5/11 point autofocus was always a bad choice but now I am definitely going to try them out a second time. Will also have to try out the manual and pre-focus method, just sounds like it will be hard when you are untrained in it.

I'm a bit sad that I keep hearing how Pentax autofocus system is less accurate compared to the other brands. Heard Nikon is best for moving objects, but it is a lot of money to invest in another brand only to use it for action photography.

03-29-2012, 04:16 AM   #17
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This I took yesterday and is one of a series of pics captured on 11 point C auto focus.
A high speed train, an boy was it flying lol
03-29-2012, 09:49 AM   #18
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Stupid newbie question - if you set it on AF.S, but the drive mode to continuous, does it lock the focus in on the first shot and then just keep taking pictures with that same focus?

If your target wasn't changing distance from you, would it be smart to actually use that as a technique, so that you didn't have to worry about having it re-focus between pictures and potentially locking on something else?
03-29-2012, 10:03 AM   #19
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11-point AF.C works the best IMO, wish there were even more...

03-29-2012, 11:54 AM   #20
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QuoteOriginally posted by SenorBeef Quote
Stupid newbie question - if you set it on AF.S, but the drive mode to continuous, does it lock the focus in on the first shot and then just keep taking pictures with that same focus?

If your target wasn't changing distance from you, would it be smart to actually use that as a technique, so that you didn't have to worry about having it re-focus between pictures and potentially locking on something else?
No.... It tracks your focussed subject
03-29-2012, 12:10 PM   #21
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On my K-5 AF.S does not change the focus in continuous shutter after it is set on initial half press of the shutter.
If you want it to change you have to use AF.C.
Also you can decide if you want the shutter to keep firing while AF is not achieved or to wait until AF is locked.
03-29-2012, 12:42 PM   #22
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Yikes... yes sorry I missed he wrote AF> S.... oops !
03-29-2012, 07:55 PM   #23
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I live on AF Single, Center Point Focus but track with the rear AF. Even at ISO 6400 from the back of the theater with SR on. Lots more here Spring Gala 2012 | Brooke Meyer

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03-29-2012, 08:29 PM   #24
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People like to hack on Pentax's AF speed, but it works fine. Try it before you give up. I use AF-C with centre point only. These were taken with a K-x, the K-5 should be much better.



03-30-2012, 03:39 AM   #25
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QuoteOriginally posted by bikecoboss Quote
People like to hack on Pentax's AF speed, but it works fine. Try it before you give up.
Im thinking same way, also!
03-30-2012, 10:47 AM   #26
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Nothing wrong with the speed of the autofucus as long as your subject is pretty big
in the frame. The focus points are huge. I cant say as Ive heard any complaints about its speed to be honnest. You get an awful lot thinking there lenses are Front or Back focussing and they are almost always nothing more than people thinking and using the red square as the focus point !
03-30-2012, 06:19 PM   #27
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One other consideration is if you're using continuous shooting mode or not. AF.C slows the shooting rate down. Here's my post from:

https://www.pentaxforums.com/forums/pentax-k-5-forum/160077-k-5-continuous-sh...ter-noise.html
Some new test results. I put on a AF lens (Sigma 17-70/F2.8-4.5) and compared AF.S vs AF.C. I think you'd be more likely to use AF.C for continuous bursts in action shooting. I also compared Centre-point and Auto focus-point selection. These tests were repeated a number of times and 2 different Class 10 SDHC cards tried.

Results with Centre-point focus are:

AF.S 6.8 fps
AF.C 4.8 fps

with Auto-focus point selection being approx 0.1 fps slower.

Burst length (raw) was usually 20 (AF.S) & 22 shots (AF.C).

The AF.C performance is still considerably better than my K20D which was only about 2.7-2.9 fps.


Ron Hendricks reports that the actual burst rate in AF.C in the field appears slows than these measurements.

I suggest that, if the subject(s) is moving tangentially (across), to use either AF.S or MF (if the distance is known e.g. on a track) to get a good burst speed.

But if the subject is moving partially or fully in a radial direction (away or towards you), then use AF.C.

It may be possible to get away with AF.S for a short burst with a subject in radial motion, depending on FL and aperture, but it's risky.

Dan.

Last edited by dosdan; 03-30-2012 at 06:48 PM.
04-04-2012, 12:28 PM   #28
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Right, so last Sunday I was out shooting mountain bikers and I did try pre-focus but not 5/11-point focus, it just didn't seem feasible due to the nature of bikers like that.

Here is an example of pre-focus here I shot 3 frames with the middle one coming out sharp enough:


Here is an example with AF.C plus single focus spot:


Afterwards I noticed that some of the pictures still seemed like they were shaken slightly, but not enough for me to think it was actual camera shake. I used a shutter speed of 1/400 or 1/500 but maybe that wasn't fast enough to avoid smearing of the subject. However I was wondering if it could be because SR was enabled when panning?
04-04-2012, 12:35 PM   #29
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You need to turn off SR if you are going to be panning, yes.
04-04-2012, 12:58 PM   #30
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QuoteOriginally posted by mikknu Quote
A big thanks for all the great replies. Have previously been lead to believe that 5/11 point autofocus was always a bad choice but now I am definitely going to try them out a second time. Will also have to try out the manual and pre-focus method, just sounds like it will be hard when you are untrained in it.

I'm a bit sad that I keep hearing how Pentax autofocus system is less accurate compared to the other brands. Heard Nikon is best for moving objects, but it is a lot of money to invest in another brand only to use it for action photography.
Nikon is the best but the pentax is no slouch. You can genraly be far more accurate with the Nikon because the focus point are about one sixth the
size too. As long as you pick a reasonable size thing to focus on in the first place the K5 is both fast and accurate.
Pre focus method is far easier than it sounds too. Its not always possable though. If you were taking pics of a 100 meter race, and you wanted
to catch that winner breaking that ribbon, prefocussing on that ribbon and hitting that shutter at the right moment will almost certainly beat shooting
10 frames a second, which could miss that precise frame even at that speed. People have been taking sports pics long before autofocus
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