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05-11-2010, 06:53 AM   #1
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K7 AF "point"selection for BIF

Hi everyone.

After searching within this forum, I am left with a couple of unanswered questions regarding the selection of the AF mode on the K7 when doing BIF photography.

As a rule, I pretty much always have the AF on "center" ... never used the center-weighed-average" nor the actual full matrix for BIF.
Also, I mostly use AF.S vs. AF.C, the latter I find rather difficult to manage. As a matter of fact, I never had good results using AF.C with either the K10D, the K20D (which I still have) nor with the K7.

I found this:
K7 AF C performance . . . BIF (8 sml images) - Steve's Digicams Forums
which discusses at length the use of the AF for BIF.

As a result, I find that my "keepers" rate is somewhat low, especially with birds flying toward me, when "panning" is out of the question. Laterally moving birds are usually not a big deal to capture if their speed is not excessive (such as with hawks and similarly fast moving birds).

So the big question is:
What is the best set up for BIF, using the K7, fitted with a DA*300/4 with and without a Pentax A-FA 1.7X adapter?

Thanks!

05-11-2010, 07:05 AM   #2
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for me, I use center AF point for focusing, I use Spot metering and always focus in the center of the bird.

I use AFC because for a moving bird, AFS does not track as well, and the shutter is interlocked with focus confrimation and will not trip . For stationary ibjects I use AF-S because camera shake (and movement of the focusing point) causes AFC to hunt.

I also turn off SR because when tracking a moving object SR introduces blurr due to it attempting to eliminate camera motion, This blurr is one dimensional in the direction of motion.
05-11-2010, 07:22 AM   #3
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First, I turn off SR (the camera has then more processing power to think about what I need most: fast AF) because anyway for action it's not really needed.

There's not much options on the K-7 for AF (interestingly, the K-x has more options: an AF-A mode and a 5-points AF mode). So for BIF I'd use AF-C and mutipoints. I found that on the K-7 multipoints works somewhat better than just using the center point. The problem with the center is that if you loose the bird for a split second from the center, the lens will hunt a lot. With multipoints, it will be smart enough to try to keep the same focus point, giving priority to the foreground subject.

For a bird coming right to you, I'm not sure the K-7 AF is good enough IMHO. You may need specialized cameras like the Canon 1D series or Nikon D3/D3s. And in general Pentax is not the best camera for action shooting, it can be done, it's just there are better tools for that.
05-11-2010, 07:39 AM   #4
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QuoteOriginally posted by Lowell Goudge Quote
for me, I use center AF point for focusing, I use Spot metering and always focus in the center of the bird.

I use AFC because for a moving bird, AFS does not track as well, and the shutter is interlocked with focus confrimation and will not trip . For stationary ibjects I use AF-S because camera shake (and movement of the focusing point) causes AFC to hunt.

I also turn off SR because when tracking a moving object SR introduces blurr due to it attempting to eliminate camera motion, This blurr is one dimensional in the direction of motion.
Thanks Lowell,
Likewise, I use center AF point focusing but I am told that this might be the cause of AF hunting during BIF photography.
Turning the SR off also means that you must use a reasonably fast shutter speed. Therefore, would it be wise to go with Tv rather than Av in this case? (I usually shoot in Av, whether it is for a moving target or a stationary one.)

JP

05-11-2010, 07:49 AM   #5
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QuoteOriginally posted by ManuH Quote
First, I turn off SR (the camera has then more processing power to think about what I need most: fast AF) because anyway for action it's not really needed.

There's not much options on the K-7 for AF (interestingly, the K-x has more options: an AF-A mode and a 5-points AF mode). So for BIF I'd use AF-C and mutipoints. I found that on the K-7 multipoints works somewhat better than just using the center point. The problem with the center is that if you loose the bird for a split second from the center, the lens will hunt a lot. With multipoints, it will be smart enough to try to keep the same focus point, giving priority to the foreground subject.

For a bird coming right to you, I'm not sure the K-7 AF is good enough IMHO. You may need specialized cameras like the Canon 1D series or Nikon D3/D3s. And in general Pentax is not the best camera for action shooting, it can be done, it's just there are better tools for that.
OK, got that now from at least two people: yourself and Lowell, above: turn the SR off.
Using AF.C in the past has been diappointing to say the least, but I will try it again with the local seagulls!
As opposed to Lowell, you suggest using the full AF matrix ... what if the bird is far enough that the AF may lock on an unwanted target? I can see that this would be ideal when the bird is close enough and with a contrast differential adequate for the AF to really lock on the target ... I am assuming.
And, would you also use Tv mode rather than Av, especially when considering turning the SR off?

I have one more situation to discuss:
there is that large hawk (a rough-legged hawk) which can be spotted often flying over farmers' fields this time of the year.
The hawk has typical brownish-beige coloring and that makes it almost "invisible" although the human eye can track it no problem.
With that in mind: a moving/camouflaged target .... how would you attempt to capture that?
Let me tell you that I have a near 100% failure rate under such circumstances.

JP
05-11-2010, 08:06 AM   #6
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Hey Jacques,
Some of the best BIF shots I ever saw posted were by a member who only used manual focus to pick a spot and shoot when the bird was in his focus area. Using a larger aperture number also gives you a larger DOF to work with. I too use Tv mode to set the minimum speed (usually around 1/750) then try for the largest ap number I can get at my chosen ISO.

I disagree strongly that you might need different equipment. This is about technique not gear.

As far as your hawk...if its too camouflaged for the camera to lock on then you go to manual. Plus that way the da*300 does not miss and recycle the entire range causing you to lose sight of the bird. Since I started using the Pentax AF 1.7x TC (another long thread) to give me a built in limiter I never lose sight if the AF misses. Now I only use manual for those coming straight at you shots. Pick a spot, focus, recompose and shoot when they get there. YMMV though. Have fun.
05-11-2010, 08:23 AM   #7
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QuoteOriginally posted by jpzk Quote
OK, got that now from at least two people: yourself and Lowell, above: turn the SR off.
There is an interesting article about VR here:
Nikon VR explained

It's for Nikon but I think it should apply to all SR systems: Do not use SR when not necessary, do not use it at all on very fast shutter speed (1/500s and above).

QuoteOriginally posted by jpzk Quote
Using AF.C in the past has been diappointing to say the least, but I will try it again with the local seagulls!
As opposed to Lowell, you suggest using the full AF matrix ... what if the bird is far enough that the AF may lock on an unwanted target?
To say the truth, I have not a lot of BIF experience (more with moving humans) and yes AF-C on the K10D and K20D was frustrating. It's better on the K-7 but it's not a miracle either. I found multipoint too slow on the K20D, on the K-7 it seems to be better for keeping the target in focus though.

QuoteOriginally posted by jpzk Quote
I can see that this would be ideal when the bird is close enough and with a contrast differential adequate for the AF to really lock on the target ... I am assuming.
But if the bird is very far, do you really need AF? Focusing to infinity may be good enough. Of course, if you're talking about birds in a cluttered environment, the multipoint may not be the best choice indeed. I had a BIF with a sky background in mind when I said multipoint was better.

QuoteOriginally posted by jpzk Quote
And, would you also use Tv mode rather than Av, especially when considering turning the SR off?
It would depend on the quality of light. But you can think about TAv also: set the shutter speed to a safe speed (let's say 1/500 or faster) and good enough aperture. When you stop down, you have more DOF and thus more margin for AF errors. A rule is that you need 2 stops to double the DOF. You may also use a slightly less long focal length and crop to again get more DOF.

And even better mode for AF speed would be manual. Once you know the light, it doesn't change a lot unless you shoot birds with much different reflectiveness or there's clouds masking/unmasking the sun. Again the camera will spend less processing power to guess the correct exposure. Manual WB can help too to reduce the CPU load.

QuoteOriginally posted by jpzk Quote
I have one more situation to discuss:
there is that large hawk (a rough-legged hawk) which can be spotted often flying over farmers' fields this time of the year.
The hawk has typical brownish-beige coloring and that makes it almost "invisible" although the human eye can track it no problem.
With that in mind: a moving/camouflaged target .... how would you attempt to capture that?
Let me tell you that I have a near 100% failure rate under such circumstances.
JP
Even with the K-7? I think it's more sensitive to low-contrast targets. But there's not much solution I can see. The only thing is to try the best glass you can with good contrast wide open, do not use TC, etc. That way the AF can perform better. You can also help the AF a little if your lens supports Quick-Shift, you can manually focus by eye close enough then let the AF do the final adjustment.
05-11-2010, 08:35 AM   #8
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QuoteOriginally posted by imtheguy Quote
I disagree strongly that you might need different equipment. This is about technique not gear.
This could start a long debate but it's obvious that it's better to nail with a hammer than with a screwdriver, although you can do it. IMHO for BIF shots, Pentax is handicapped by 2 things: lack of great AF and lack of long and fast glass. This is not to say that in its class, it not good, but Pentax doesn't offer anything above the K-7 class of camera.

05-11-2010, 09:17 AM   #9
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There have been already some solid, strong opinions. I wish simply to add my experience.

I use typically AF-C, Centre focus, and I add Hi continuous shooting. I found that I can improve my success rate, using a burst of 4-5 shots than a single shot.

I agree with an earlier post that AF becomes meaningless when the bird is in the far field. MF would work better: e.g, being set a infinity as default. Two years ago, I shit some buzzards circling over a field with a blue sky on the background. The MF worked great then.

Hope that the comment will assist...
05-11-2010, 09:44 AM   #10
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Hi Jacques,

That was an early post, pretty much just after I got the K-7.

Things I discovered after that:

The focus limiting of the 1.7x AFA is good for BIF distant enough that you can set the lens at infinity and leave it there -- the increased speed to acquire is helpful, but the extra magnification makes the acquisition in the viewfinder more difficult, and when the bird gets closer than the limited focusing range, it's hard to recover focus manually while tracking the bird. This is a technique thing, so with practice, it could get easier, but as I mentioned, I don't shoot a lot of BIF, so have not developed the technique. I've heard from the best BIF shooters I know that a 400 f5.6 lens on a 35mm camera is about the sweet spot for this purpose, for both acquisition and handling, and have had about the best results with my FA*300/4.5, so I'll agree (450mm f4.5 eq).

I've tried my Pentax and Sigma AF 300/2.8s, thinking that the increased speed would give the AF system more light to work with, but the shallow DOF wide open for focusing works against you -- as does the extra mass of the lens, even on a gimbal/tripod.

In AF C, it's very important to get an initial focus lock beep before you start a continuous string. If the first shot isn't in decent focus, the camera will have trouble gaining focus during the string.

Since my technique is lacking, and I have trouble keeping a bird in the center of the VF, I've had the best success with multipoint. There's a downside though -- Continuous High slows down to @ 3FPS. Center or Select point focusing allows greater frame rate, but I've found that, for me, multipoint gets me better results. Use as few "Auto" functions as possible to give the AF system and continuous shutter as much processing power as possible. I use multipoint focusing, Av priority (because panning will give you varying light), and AF C as the only "Auto" features, but if you can track a bird consistently in any single part of the frame, Center or Select will give you close to the full 5+FPS.

Choose a relatively high ISO and a reasonably small aperture to get shutter speeds that will at least have a chance to stop motion. Deeper DOF makes the AF system's job easier.

I've never turned SR off for this, but can't argue that it wouldn't give better results, both in focusing speed and frame rate. With relatively high shutter speeds to freeze subject motion, I don't think SR adds much to the mix, and it might detract from some of the other performance parameters, but I've not experienced SR induced blur because of the panning -- YMMV.

I've gotten as many as 19 shot sequences of gulls and Caspian Terns in flight with the K-7. I believe my record with the K20 was more like 6. Most show very good focus, but all were very usable, and with generally better focus than the K20. The improved tracking ability from the shorter blackout times is very noticeable. For me, the K20 is considerably better than the K10, but the K-7 is much better -- especially since SAFOX has been pretty universally panned for AF C performance.

For strings of an approaching bird (the best ones, IMO) I always start with the lens focused to infinity -- there's a lot less focus ring throw at distance, so the AF has less work to do to get the initial focus. After each string, I point at the sky and let the AF take the lens to infinity before I even start to look for the next subject.

I'm in the process of adding an external gun sight to the hood of my FA*300 (no, not permanently!) -- cannibalizing a cheap Daisy Red Dot for the hood and front reticle. I've tried it just jury rigged to sight birds in trees with my left eye, while my right eye is at the VF. I think this might help me get faster VF acquisition, and may even be a better way to track moving birds since there would be no blackouts.

I'll repeat the caveat that I'm neither an experienced, nor even a good BIF shooter.
Hope these tips might help some. . .

Scott

. . .and sometimes you just get lucky. . .This one is with either the Tamron 70-300 or the Tokina 80-400 at 180mm, cropped a bit.
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05-11-2010, 10:05 AM   #11
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there area lot of interesting ideas here

full AF matrix , while I agree might be good when a bird is close and fills the view finder, generally when you are tracking a BIF it starts a long way away and in the view of only one sensor at a time, the others on something else usually the infinite bluy sky

the use of the 1.7x AF Adaptor is also true it focuses quickly within the limited range of focus, but you need to continually move this range when tracking.

As for a bird coming right at you, I have to disagree about pentax's AF ability. See the shot below done with a PZ1, and the K300F4 plus 1.7x AFA adaptor. I think it works pretty well.



while SR does require increased shutter speed to eliminate camera shake, it does nothing to freeze motion, that always needs shutter speed. Panning helps, but as I said, it also leads to blurr when SR is on.

MF for distant subjects is also a valid idea, but many many AF lenses have limited focus trhow in MF mode, my sigma 70-200F2.8 for example has only 90 degrees, against my SMC300F4 with over 300 degrees. using an MF lens with a gradual focus throw is good when subject is at a distance and moving in, it is easy to track and keep focus, the issue is speed of aquiring focus. AF is faster when starting from the opposite end of the focus throw,
05-11-2010, 10:43 AM   #12
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QuoteOriginally posted by hcc Quote
...... Two years ago, I shit some buzzards circling over a field with a blue sky on the background.
I think you just lightened up the tone of this whole thread with your admission of avial intestinal problems. Thanks for NOT including pictures.
05-11-2010, 11:01 AM   #13
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QuoteOriginally posted by Lowell Goudge Quote
the use of the 1.7x AF Adaptor is also true it focuses quickly within the limited range of focus, but you need to continually move this range when tracking.
I can help clarify this for those not familiar with this TC. Shooting with the AF 1.7x and a da*300/4 for example at f/11 (displayed), I can set the limited focus range so that it begins and ends about where all the action will be. Yesterday for Ospreys, I adjusted for a minimum focus of about 40m and the maximum was almost to inifinity, 300m maybe. Certainly way beyond any shot I would take.

My point being that you can set up a single large focus range in the big outdoors. Now obviously for little birds on a feeder at 8m the focus range is only good for the depth of the feeder and requires a manual adjustment to focus on a branch at 10m. But I much prefer that over a TC (or bare lens) that may allow the lens to do a complete cycle if you lose the focus point for a second.
05-11-2010, 12:36 PM   #14
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QuoteOriginally posted by jpzk Quote
As a rule, I pretty much always have the AF on "center" ... never used the center-weighed-average" nor the actual full matrix for BIF.
Some confusion here: neither 'center weighted average" nor "matrix" have anything whatsoever to do with focus. They are *metering* methods. The method you use for selecting focus point has *nothing* to do with the method you use for metering - they are two totally independent settings. Do be sure you are actually controlling the one you want.
05-11-2010, 05:03 PM   #15
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QuoteOriginally posted by imtheguy Quote
Hey Jacques,
Some of the best BIF shots I ever saw posted were by a member who only used manual focus to pick a spot and shoot when the bird was in his focus area. Using a larger aperture number also gives you a larger DOF to work with. I too use Tv mode to set the minimum speed (usually around 1/750) then try for the largest ap number I can get at my chosen ISO.

I disagree strongly that you might need different equipment. This is about technique not gear.

As far as your hawk...if its too camouflaged for the camera to lock on then you go to manual. Plus that way the da*300 does not miss and recycle the entire range causing you to lose sight of the bird. Since I started using the Pentax AF 1.7x TC (another long thread) to give me a built in limiter I never lose sight if the AF misses. Now I only use manual for those coming straight at you shots. Pick a spot, focus, recompose and shoot when they get there. YMMV though. Have fun.
Lee,
Before I go ranting about my afternoon experience with AF.C, let me tell you that I will indeed try your suggestion (again) with my Pentax A-FA 1.7X with the DA*300/4. I did test that a while back but I found it difficult to get focus "dead on".

Anyway, here goes:

This afternoon .... took the K7/DA*300 out, set it on Tv, AF-C, spot metering, centre AF, ISO at 320 (was a sunny day) and shutter speed at 1/1000s. Aperture went from F8 to F11. SR off.
Took a couple of test shots on gulls ... not in focus.
Took a couple of test shots on crows ... not in focus.
Decided to return to AF-S ... tested on gulls again: better but not dead-on focus.
So, I returned to my old way: Av, AF-S, SR ON ... better focusing!?!?!

And ... using Tv mode made ALL my photos UNDERexposed! ... what the heck?

Thanks for the reply.
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