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10-11-2015, 01:59 PM   #1
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Increasing AF speed on a K-3 : technique or hardware or both?

My kid's school hosts a yearly Walk-a-Thon to raise money for projects and supplies. Last year I did it with a K-30 and I was very "gentle" in my approach. I didn't use AF-C too much, I didn't pan and track kids running, and I asked kids to freeze and hold a pose. This year I used my K-3 and I was significantly more "aggressive". I used AF-C a lot, I panned while tracking the kids, and I didn't ask kids to freeze as much. My keeper rate and general IQ was about the same between the two years. This is good considering my more "aggressive" use of the K-3. For as much improved as the K-3's AF speed was this year over the K-30's, I wish it were faster. I had a good number of completely missed shots where the camera and lens hunted. I heard a lot of "Vvvvzzzt-vvvvzzt-vvvt!" without the "schnick-schnack" of the mirror and shutter. Sometimes the shutter would fire after achieving focus but the kids had moved far enough out of focus that the shot was missed. I tried to alleviate this by shooting in TAv mode with my aperture set to f/8, shutter speed to 1/1000th, and I let ISO float. My thought was that the increased DoF would compensate for the change in the kid's position during the camera's response time. The K-3 had a very hard time tracking kids running toward me but did easier with kids running across my field of view and those running away from me.

One thing I forgot to do was turn off Shake Reduction. I'm sure this messed with the camera's ability to focus and maybe contributed to a little softness in some images. Next year.

Oh, I was using a DA 18-135mm. My target is an album of 4" x 6" prints with a few 8" x 12" special prints so my resolution requirements are pretty low.

I would like to increase my AF tracking performance and lock-on time. Can anyone offer any hints on how to do this? How do I approach an event with 500 kids running laps around a field for an hour and a half? Is there a setting I can enable or disable? Is there a faster focusing lens I need to look into?

Thanks!

10-11-2015, 02:15 PM   #2
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QuoteOriginally posted by 6BQ5 Quote
One thing I forgot to do was turn off Shake Reduction. I'm sure this messed with the camera's ability to focus and maybe contributed to a little softness in some images. Next year.
There should be no reason to do this.

My suggestion would be to keep working on your technique. Adjust the AF manually when needed. Also, the 18-135mm has pretty fast AF but the aperture is slow. You might be better off with a lens like the Sigma 70-200mm F2.8, or even the Tamron if you don't mind the noise. After all, the less light there is, the longer the AF system takes to calculate proper focus.

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10-11-2015, 02:17 PM   #3
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Interesting question. I also have a K-3, and I also asked myself how to improve AF lock and tracking. One of things I noticed is that when out of focus, the AF move into a default direction: from far to close. So, by pre-focusing at infinity (quick shift makes it easy), or just behind the target (if the target position is known in advance), the K-3 is able to lock fairly quickly without hunting, then tracks the target. The K-3 AF is hunting when the out of focus is initially in front of the target, then the AF goes forward and again backward to find the target, which takes a lot of time. That's also why I guess that Ricoh implemented a AF position memory on the DFA 150-450, for instance, to preset the AF to a certain position. I use focus preset a lot with my K-3 + DA*300 combo, it works very well.

Last edited by biz-engineer; 10-11-2015 at 02:27 PM.
10-11-2015, 02:33 PM   #4
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Is there any way you could just manually focus on a spot before the kids get there and rely on depth of field? Have a few such spots picked out and you might just have the answer.

10-11-2015, 03:22 PM   #5
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I found that when tracking it helps to follow the subject for a moment, then shoot. If you hold down the shutter it doesn't seem to have time to track and focus. As well as putting the continuous shooting to medium or low.
10-11-2015, 05:08 PM - 1 Like   #6
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I also have a K3 and have photographed my children's sport for many years particularly basketball and Australian Football (which is like basketball except on a large outdoor field and the ball is kicked). In the Aust Football you have young men running in all directions at full speed so it is test for the AF and the skill of the operator.


My setup and tips for maximising the keeper rate (I use the DA*300mm but I would do the same with your lens/situation):
1. AFC and Sel 4 (I use the centre point). Also all the menu AF settings set for focus priority.
2. TAv to control shutter speed and DoF but I like to keep the ISO below 800 if possible. With kids running and 135mm I would guess that you need to keep your shutter speed above 1/350 (preferably 1/500+) and Aperture F4 to F8 to keep iso 200-400
3. I find Back button focus to help significantly, takes a little practise but once you've got the hang of it you don't ever go back to the shutter release focus (or need to use AFS)
4. I also employ the Continuous Hi shooting and take 2-4 shots in each burst. This helps with getting an unobstructed shot with eyes open etc
5. Shooting in Portrait rather than Landscape orientation?


The technique that I have found that works for me is:
1. to have the lens pre- focussed at around the distance where you are expecting to capture the action ie reduce the need for the lens to travel a long distance to the focus point. If your subjects are on an aths track then pre-focus on the track where you expect the runners to be
2. when taking the shot, centre the view finder on the target's chest and start tracking it in the viewfinder ie maintain the target in the centre of the viewfinder for a second. Then hit the AF button and then hit the shutter for 3-4 shots. I guess there is 0.25-1.0 second between the AF and the shutter but it gives the AF a small amount of time to do its work before the shutter triggers. Keep the AF button pressed for the duration of the shooting and also keep the target area centred in the viewfinder. When you get the AF point lighting up and the audible ping and the shot taken then you know you have nailed the shot (but I mostly don't notice this and I would expected you would get 80+% of your shots in focus doing this whether you see the AF light up or not).
3. Subjects running towards you are more difficult but still doable - better to get your subjects moving laterally if possible but don't let that stop you doing the head on shot.


Good luck with it - there is as much technique as camera settings in getting keepers of action sports so you'll find a little practise goes a long way towards success.
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10-11-2015, 06:03 PM   #7
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Interesting suggestions RedBoomer, and great shot. I'm saving up for a fast long lens, and must remember to try your setup.
10-11-2015, 06:24 PM   #8
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Thanks for the replies, everyone!

Pre-focusing sounds like a good idea! I don't know how well I could have done this though. I was in the field walking with the kids catching everything I can. Imagine someone standing in one of those wind tunnel booths that blows around $20 bills and you have 60 seconds to grab as many as you can! Anyways, by the time I could have set myself up and prefocused the moment will have passed. Although the event is called a "Walk-a-Thon" the kids always turn it into a "Sprint-a-Thon"! The grand prize was a Fitbit.

There were a couple of spots, literally 2-3, where I could prefocus so I shouldn't discount this technique.

Could I have set the camera in manual focus mode and enable Catch-in-Focus? I prefocus on the ground, recompose so a blurry tree is in the center of my viewfinder, and then when a kid runs by and triggers the focus confirmation I get a picture.

@Adam : what is this Sigma 70-200mm lens you are referencing? I could not find this one in a Pentax mount. Tamron's 70-200mm looks interesting and seems to be a current/active product. I'll have to dig into this. It seems like its an APS lens.

@biz-engineer : that's a great observation! I never paid attention to which direction the camera drives the focus. With that in mind, I could turn the quick shift to infinity and let the AF system do the rest. Maybe this would eliminate some of the hunting.

@RedBoomer : great explanation and sample! Thanks! I figured out to turn on high continuous burst mode at the end to capture a water balloon toss at the school principal. Shooting two eyes open I can see when the kids would toss the balloon and I would click off 4-5 quick shots. What a life saver! I didn't think about it earlier during the run. Does the camera refocus for every shot in the burst?

10-11-2015, 07:27 PM   #9
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QuoteOriginally posted by 6BQ5 Quote
@Adam : what is this Sigma 70-200mm lens you are referencing? I could not find this one in a Pentax mount. Tamron's 70-200mm looks interesting and seems to be a current/active product. I'll have to dig into this. It seems like its an APS lens.
The Sigma 70-200mm F2.8 OS HSM has now been discontinued, but it was available for a few years. It's quite good. (all the 70-200's are FF)

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10-11-2015, 07:38 PM   #10
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QuoteOriginally posted by 6BQ5 Quote
Thanks for the replies, everyone!

Pre-focusing sounds like a good idea! I don't know how well I could have done this though. I was in the field walking with the kids catching everything I can. Imagine someone standing in one of those wind tunnel booths that blows around $20 bills and you have 60 seconds to grab as many as you can! Anyways, by the time I could have set myself up and prefocused the moment will have passed. Although the event is called a "Walk-a-Thon" the kids always turn it into a "Sprint-a-Thon"! The grand prize was a Fitbit.

There were a couple of spots, literally 2-3, where I could prefocus so I shouldn't discount this technique.

Could I have set the camera in manual focus mode and enable Catch-in-Focus? I prefocus on the ground, recompose so a blurry tree is in the center of my viewfinder, and then when a kid runs by and triggers the focus confirmation I get a picture.

@Adam : what is this Sigma 70-200mm lens you are referencing? I could not find this one in a Pentax mount. Tamron's 70-200mm looks interesting and seems to be a current/active product. I'll have to dig into this. It seems like its an APS lens.

@biz-engineer : that's a great observation! I never paid attention to which direction the camera drives the focus. With that in mind, I could turn the quick shift to infinity and let the AF system do the rest. Maybe this would eliminate some of the hunting.

@RedBoomer : great explanation and sample! Thanks! I figured out to turn on high continuous burst mode at the end to capture a water balloon toss at the school principal. Shooting two eyes open I can see when the kids would toss the balloon and I would click off 4-5 quick shots. What a life saver! I didn't think about it earlier during the run. Does the camera refocus for every shot in the burst?
The pre-focus is not essential just speeds up getting to the focus point. It also just a very quick focus on something at about the right distance so it takes no time to do. I find that even with long-throw, slow focussing lenses eg the DA* 50-135, if you are close to the right focus when you make the shot then the lens is still very fast to make focus. The pre-focus avoids (reduces?) the lens hunting.


Does the camera refocus for every shot on continuous? It is not 100% perfect but the camera tries to re-focus between shots and to follow (track) the target identified in the first shot - but you must keep the AF button pressed otherwise the focussing action will stop until the AF is pressed again. On longer continuous bursts, the camera can lose focus (which you can see in the view finder) in which case you can lift off the AF button momentarily, re-centre the target in the viewfinder, re-press the AF button and recommence shooting. This becomes second nature with a bit of practise.
10-11-2015, 08:40 PM   #11
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QuoteOriginally posted by Adam Quote
There should be no reason to do this.

My suggestion would be to keep working on your technique. Adjust the AF manually when needed. Also, the 18-135mm has pretty fast AF but the aperture is slow. You might be better off with a lens like the Sigma 70-200mm F2.8, or even the Tamron if you don't mind the noise. After all, the less light there is, the longer the AF system takes to calculate proper focus.
QuoteOriginally posted by RedBoomer Quote
The pre-focus is not essential just speeds up getting to the focus point. It also just a very quick focus on something at about the right distance so it takes no time to do. I find that even with long-throw, slow focussing lenses eg the DA* 50-135, if you are close to the right focus when you make the shot then the lens is still very fast to make focus. The pre-focus avoids (reduces?) the lens hunting.


Does the camera refocus for every shot on continuous? It is not 100% perfect but the camera tries to re-focus between shots and to follow (track) the target identified in the first shot - but you must keep the AF button pressed otherwise the focussing action will stop until the AF is pressed again. On longer continuous bursts, the camera can lose focus (which you can see in the view finder) in which case you can lift off the AF button momentarily, re-centre the target in the viewfinder, re-press the AF button and recommence shooting. This becomes second nature with a bit of practise.
I experimented a bit with focus tracking and I have to say that I am disappointed with the current behavior of my K-3.

Since I don't have kids running toward me I decided to walk toward something stationary in my house. AF-C was turned on and I used a low burst rate. Once the first shot was focused and taken I started walking toward my fixed object. The K-3 kept firing away and claiming the AF was good and locked although, as you mention above, the image is clearly out of focus. I stop to give the K-3 a chance to detect that focus is lost so it can recover. No such recovery happens. The K-3 keeps clicking away thinking all is well. If the AF module was confused then the focus lock indicator blinks. Ok, no problem. So I stop again and let AF recover. It does not. During this time the camera keeps firing the shutter recording garbage. I double check my settings to ensure I have focus priority enabled.

This behavior is kind of useless to me. I can get can bursts of 100's of images of nothing. The result is an overflowing buffer and two SD cards that can't swallow all that data in a timely manner. When I link focus functions to the shutter button being half way pressed then I am at least saving myself an extra finger motion and press.

What am I doing wrong? Perhaps I should do this tomorrow in bright outdoor light. I can pan the camera and watch for AF confirmation prior to the shutter firing.

On the bright side I tried throwing my focusing toward infinity prior to some single frame shots. Oh wow, much faster AF performance compared to starting off somewhere random! Forget AF-C. Just use AF-S like this and call this the best I'll get??
10-11-2015, 09:28 PM   #12
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QuoteOriginally posted by 6BQ5 Quote
The K-3 kept firing away and claiming the AF was good and locked although, as you mention above, the image is clearly out of focus.
My K-3 AF exhibits the same behavior in AFC tracking when there is no distance separation between the subject and the background (along the 3rd dimension).
AFC tracking uses the difference of focus between in-focus AF point (the one locked) and adjacent out of focus AF points, and this is not exclusive to Pentax DSLR camera (same with a 7D). Therefore, when doing a AFC tracking test with adjacent AF points located in the same X,Y plane, the differential focus is zero (or at least lower than a threshold) and therefore the AF algorithm can't decide what to do. In this case, it's not surprising that AF is confused, not able to track. But when there is a significant depth between in-focus and out-of-focus, such as when tracking birds in flight, the K-3 AFC tracking works very well. In addition, faster lens provides more sensitivity between out of focus area and in-focus area. There's also the AFC hold parameter to be set for tracking.

- AF tracking of a moving subject requires depth between the subject and background.
- not all active AF points (e.g 9 points, 25 points) should cover the subject, otherwise again there's not difference of focus between AF points.
- a faster lens such as Sigma 70-200 f2.8 HSM (or the future DFA 70-200), would provide better AF lock and tracking.

But the fact that the K-3 still takes shots, with focus priority is selected, is IMO a firmware bug. To be honest, I'm a bit disappointed, that Ricoh does not provide any detailed guide regarding how to best use the AF and AF modes, for what it would cost them to write a white paper about that...

Last edited by biz-engineer; 10-11-2015 at 11:00 PM.
10-12-2015, 01:16 AM   #13
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Boris, sorry to hear you are not getting satisfactory results. I would fully expect to be able to get 95% of shots in focus of kids running past on a track in good light and you should be able to as well?? I would not even consider using AFS for moving subjects as it more or less guarantees that shots will be out of focus if the subject/camera distance changes. I had a look a quick look in my files for an example of tracking a person moving towards the camera and found the attached series of a basketballer running toward the camera (at a medium jog). These were taken with the DA* 50-135, F2.8, 1/350s and iso 1600-3200. (pretty bad light!) using AFC and the technique I described.. Shots taken raw, converted to JPG in LR5 and no other processing except for the last one which is slightly cropped and cleaned up. The photos are all in good focus and the player moved 50' up the court towards me so despite the poor light the camera did a really good job. It's not 100% every time but I get many good photos using AFC on moving subjects. I'd recommend you try in daylight with your lens on F4 or F5 and see if you can get a few keepers. All the best. Geoff
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10-12-2015, 02:24 AM - 1 Like   #14
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QuoteOriginally posted by biz-engineer Quote

But the fact that the K-3 still takes shots, with focus priority is selected, is IMO a firmware bug. To be honest, I'm a bit disappointed, that Ricoh does not provide any detailed guide regarding how to best use the AF and AF modes, for what it would cost them to write a white paper about that...
There a big different between priority and mandatory !!

The only difference between focus priority and shutter priority is the weighting applied to focus Vs shutter

Both will attempt to focus the camera using all the data you provide, In the case of single point and approaching target that would be roughly no data so no accurate focus will occur the same is true for lacking target background separation.

So from this we can establish 1 rule - single point AF does not allow predictive AF

In focus priority the camera will attempt to focus the subject to the detriment of FPS so under low light frame rate will drop drastically as it can take upwards of .7 second for the sensor to correlate multi point AF, Under shutter priority the camera will fire the shutter while it attempts to focus so frame rate around 7.2 will be achieved.

Another rule coming up

Under AF-C focus is not promised as this is a continuous AF mode the camera will always be attempting to follow the moving subject , If you need lock before shutter then AF-S is the mode you should use.

Finally Lens, as AF-c relies on fast reporting from the Phase detectors and positive discrimination of target vs background it easy to see the slower the lens the worse AF-c performance, When light drops the phase reporting takes longer, an f2.8 lens lets in twice the light as an F4 lens so you can see under low light a fast lens is required.

Under good light you will still need a fast lens especially with shorter focal lengths as the DoF can end up so large practically everything is more or less in focus and AF-c is pointless and wont work anyway.

Nothing has changes you still need a 70-200 f2.8 as a starter for indoor sports work (aps-C you can get away with 50-135) for intimate action shooting you need f2.8 or better or your wasting your time.

IMO no lens in the 10-200mm range should be used for indoor sport AF-C work unless it has an open aperture >=f2.8 physics clearly shows you will be disappointed !!

Only when you've met the above requirements is it time to look at body used or lens motor speed.

Of cause in reality you look at both the basics requirements (F2.8 and 200mm) at the same time as lens /body performance, With this in mind and the knowledge that glass control is paramount to good AF-C performance you need high torque low latency lens drive which translates to HSM,SDM,DC in lens drive.

Currently the best current indoor sport solution (basic) for Pentax is
DA* 50-135 + K3ii

the best 2nd hand solution is
Sigma 70-200 OS HSM f2.8 + K3ii

This is only valid for 'general' advice for indoor shooting and is possibly not correct for your sport/conditions.

For example I shoot under mixed lighting in 25 and 50 m Pools sometimes deck side my usual 'arsenal'

25M pools
DA*300 F4 , 70-200F2.8 , 50-135 F2.8 and 55 f1.4
50M pools
DA*300f4 , Sigam 400 F5.6 , Bigma +HD converter

I usually carry the 70-200 @50M pools as sometimes the light is appalling as night comes, Generally 50M pools in the UK are modern and well lit.

---------- Post added 12-10-15 at 10:35 AM ----------

QuoteOriginally posted by RedBoomer Quote
Does the camera refocus for every shot on continuous? It is not 100% perfect but the camera tries to re-focus between shots and to follow (track) the target identified in the first shot - but you must keep the AF button pressed otherwise the focussing action will stop until the AF is pressed again. On longer continuous bursts, the camera can lose focus (which you can see in the view finder) in which case you can lift off the AF button momentarily, re-centre the target in the viewfinder, re-press the AF button and recommence shooting. This becomes second nature with a bit of practise.
Just thought on your last bit, Getting multiple AF reading is paramount for successfull Predictive AF (sharp image under AF-C) fro this to occur the Photographer must.

1 keep AF wound up
2 accurate track the subject

It may be easier for a beginner to enable back button AF and keep that pressed , That way they can 'squirt' the shutter in bursts without lifting to far and stopping AF tracking. allowing more time to concentrate on keeping the subject on sensor.

---------- Post added 12-10-15 at 10:43 AM ----------

QuoteOriginally posted by RedBoomer Quote

My setup and tips for maximising the keeper rate (I use the DA*300mm but I would do the same with your lens/situation):
1. AFC and Sel 4 (I use the centre point). Also all the menu AF settings set for focus priority.
.
Centre point ? You've disabled predictive AF, so as soon as you lose target or the camera/lens can't keep up with the action you will get OOF images

If you used 9 point expanding you'd get predictive AF and auto handoff if you slightly lost the subject from the centre point during the pan the camera would hold target for you

Admittedly Pentax's 'predictive' AF is pretty crude but works well for linear tracking allowing sharp image as the AF will skip to where the subject will be whilst the shutter is open not lagging behind.
10-12-2015, 04:53 AM   #15
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@ awaldram: Thanks a lot for the detailed clarification. So, if I understand correctly, since longer focal lengths yield less DoF, full frame might potentially work better for AF accuracy and tracking?
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