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05-12-2009, 03:54 PM   #1
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When to use auto-select focal points for BIF

I have been practicing Birds In Flights shots using Pentax F* 300mm f/4.5. I normally use AF.C along with center focal point and pan the bird movement. Last weekend, I tried out AF.C and auto-select focal points and let the camera to pick 1 of the 11 focal points for me. It works harder than center focus but not working well all the time. The worse experience happens when AF foul up on me when I shoot a "Tern" related birds in a continuous half-press on shutter while hitting shutter for the shots

Summary of my settings
  • AF.C
  • ISO 500 to 640
  • aperture in between f/6.3 to f/9.0
  • shutter faster than 1/1000 sec
  • SR off
  • auto-select AF points
  • single shot drive mode

The good experience
It usually work across the water in the lake or a plain sky when the bird contrast is detected by the AF. The AF in auto-select AF points seem to work harder than single center AF point. I hear the motor noise grinding across different points trying to obtain a focus.

The bad experience
When the bird glide over a mountain or some background with perhaps distracting color and contrast in the background, AF hits and miss-focus on the background, Also the motor noise from my F* 300mm create quite a chaotic scene for the photographer.

worse experience: AF refuses to lock in focus
But I ran into cases that AF halt to move on when I continue to half-press the shutter in tracking the bird movement along with shutters in between beeps. This happens usually after I hit the shutter couple of times when the AF points are confirmed. I have my AF button programmed for "canceling AF" but I don't think I hit that button. It happens at lease 5+ times that I totally lose the AF mechanics and have to point my lens to ground and half-press to reset everything back to normal.

Later in the shooting, I completely turned to MF. Do you have similar experience when the AF lock up and refuse to focus for you? This is my first time in daytime shooting that AF foul up on me.

Thanks,
Hin


Last edited by hinman; 05-13-2009 at 10:40 AM.
05-12-2009, 04:06 PM   #2
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Some shots that work, but I have many that are off-focus either to the background or not having a focal point in focus in the final picture.

#1 (MF)



#2 (MF)
user frame error



#3



#4



#5



#6



Last edited by hinman; 05-13-2009 at 10:16 AM.
05-12-2009, 04:15 PM   #3
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Nice shots of a tern! They are pretty quick and can be hard to capture.

I prefer shooting with the center point on most cameras except for my 1DsII which has a huge pile of AF points on it -- on cameras with 9 or 11 I find that they are too far spaced apart to work really well in servo/tracking mode.

That said, lately I've been stuck using the center point only since with a 1.4x converter on my 400/5.6 only the center point is active (the only one sensitive to f/8).
05-12-2009, 06:11 PM   #4
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QuoteOriginally posted by pingflood Quote
Nice shots of a tern! They are pretty quick and can be hard to capture.

I prefer shooting with the center point on most cameras except for my 1DsII which has a huge pile of AF points on it -- on cameras with 9 or 11 I find that they are too far spaced apart to work really well in servo/tracking mode.

That said, lately I've been stuck using the center point only since with a 1.4x converter on my 400/5.6 only the center point is active (the only one sensitive to f/8).
Thanks for the inputs. I have not thought of the issues that the focal points from 9-11 may be too far apart.

There are two times that I tried to use AF.C along with auto-focal points.

I have mixed results more towards a lot of off-focus shots. I do not post the bad shots into flickr or my blog post. In the time with three puppies running around in about 5 to 20 feet distance, almost all of my shots from auto-select AF points are off-focus and I ended up changing back to AF.S and center focus. This time on the tern in flight about a good 40 feet+ distance, I have some keepers but the AF motor grind to a halt and I need to reset a couple of times by half-pressing shutter with lens pointing to the ground.

I don't know if my problem comes from careless full shutter release in AF.C as AF.C allows you to release shutter even when focus is not locked. My timing in hitting shutter after AF beep may be off, don't quite know unless I can easily analyze the EXIF to learn about my mistakes in the shots. I need to work on my peculiar AF issues as there are great chances that I mis-use the intended features. Or perhaps, the AF.C along with auto-select AF points don't work well for certain cases.

Thanks,
Hin


Last edited by hinman; 05-12-2009 at 06:30 PM.
05-12-2009, 07:19 PM   #5
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I've found (like you) that the auto focus points work well when there isn't anything to confuse them. If there is then it really is hit or miss when the camera tries to guess what are you trying to focus on.


John
05-12-2009, 07:41 PM   #6
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QuoteOriginally posted by hinman Quote
I have been practicing Birds In Flights shots using [URL="http://techtheman.blogspot.com/2009/05/pentax-f-300mm-f45-on-terns.html"]Pentax F* 300mm f/4.5

Thanks,
Hin
Is that your new lens? Count me one of the envious bird shooter as well.

Suggestion to you for improving keeper rate while using AF-C

1. Manual exposure
2. fix the iso at 800 or even 1600
3. manually set the focus distance to infinity before shooting AF which prevent the lens hunting the other way while focusing

See how it works

I recall you had quite a few impressive bif shots as well maybe with another lens.

QuoteQuote:
Later in the shooting, I completely turned to MF. Do you have similar experience when the AF lock up and refuse to focus for you? This is my first time in daytime shooting that AF foul up on me.

Been there 3 years ago. But I was using DL not K20D
With tern and small birds flying real fast and close, getting the birds in the frame, not to mention in the middle of the frame, is tricky already. The smallest bird that I can do MF is with sea gull.


QuoteOriginally posted by hinman Quote
Some shots that work, but I have many that are off-focus either to the background or not having a focal point in focus in the final picture.
[center]
#1
Like your first image. There is big dispute as to whether you should stick to center or AF points while you are panning . If you move too fast and your cener point actually points at the sky for a split second, then you cannot blame the camera for back focus. And I doubt you can direct the bird in what direction it should fly.

A bigger bird flying in a predictable pattern is , I would say , a lot easier even in MF. My manual lens can never back focus to infinity when I was tracking the flying subject. If I nail the bird in the eye while doing MF, I will never BF or FF. But if you leave your AF camera to direct you, you will 100% BF or FF in this one (even 1DMIII or D3x)










Daniel

Last edited by danielchtong; 05-13-2009 at 10:05 AM.
05-13-2009, 10:22 AM   #7
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QuoteOriginally posted by palmor Quote
I've found (like you) that the auto focus points work well when there isn't anything to confuse them. If there is then it really is hit or miss when the camera tries to guess what are you trying to focus on.

John
John, thanks for the inputs, the AF.C and auto-select AF points do work reasonably well in some cases such as these shots when the neighboring scenes have no competing contrast for the AF mechanics to pick up the focus. It rightly picks up the bird.



above sea






But I do have the most problems when the bird approaches me head-on from a distance or when trees and mountain backdrop are involved in the flight path. If the bird is on a horizontal flight path such as the above two shots, it is easier to achieve focus but not the other case when the birds are approaching me from a distance. I find the most problems in AF being slow in the first shot.

As Daniel has rightly suggested, MF to infinity to help the AF in quickly picking the first shot. But that may not be possible with my F* lens as I need to toggle two switches -- one of the MF/AF ring on the lens and one on the body. When I finish the two switches, the bird are likely gone and likely laughing their hearts out.

Hin

Last edited by hinman; 05-13-2009 at 10:29 AM.
05-13-2009, 10:34 AM   #8
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Daniel,

I will reply in more detail. I wish I can join you for a photo tour on the birds. There is so much to learn from you. Will be back to share more information.

After examining many of my failed shots in AF.C with auto-select focal points, I find some mistakes do come from me pressing the shutter too soon. In AF.C, I think I lose the trap focus and user errors are prone to happen.

But there is one thinking that I have -- the AF fouls up more often when the birds are approaching me heads-on from a distance.

More to follow soon.

Hin

05-13-2009, 10:55 AM   #9
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QuoteOriginally posted by hinman Quote
I find the most problems in AF being slow in the first shot.

As Daniel has rightly suggested, MF to infinity to help the AF in quickly picking the first shot. But that may not be possible with my F* lens as I need to toggle two switches -- one of the MF/AF ring on the lens and one on the body. When I finish the two switches, the bird are likely gone and likely laughing their hearts out.

Hin
We all know that the first focus lock is important

You only need to toggle the two switches twice.
First you switch both to MF and move the focus to infinity.
Then you turn both switches AF.
Then you wait until your subject is around 120 feet away (for 300mm lens) before you actuate the AF-C by pressing the shutter in full and firing in burst and following the birds in flight.
Critical for you to have a fast card.
There is no reason why you should press the shutter for each shot as your action consists of only a few seconds. Each time you press it vibration is brought to the camera.

Gee pl neglect what I said above as it only applies to the case of DA300mm with its sdm following the subject.

Daniel

Last edited by danielchtong; 05-13-2009 at 11:03 AM.
05-13-2009, 11:09 AM   #10
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QuoteOriginally posted by danielchtong Quote
We all know that the first focus lock is important

You only need to toggle the two switches twice.
First you switch both to MF and move the focus to infinity.
Then you turn both switches AF.
Then you wait until your subject is around 120 feet away (for 300mm lens) before you actuate the AF-C by pressing the shutter in full and firing in burst and following the birds in flight.
Critical for you to have a fast card.
There is no reason why you should press the shutter for each shot as your action consists of only a few seconds. Each time you press it vibration is brought to the camera.

Gee pl neglect what I said above as it only applies to the case of DA300mm with its sdm following the subject.

Daniel
Daniel, thanks for sharing the tips. I have been using single shot drive mode, I should try your suggestion on firing shots in burst. And if I have the money, I would love to have both the F* 300mm f/4.5 and DA* 300mm f/4.0. I picked the Pentax F* 300mm f/4.5 due to the smaller size and weight and I still prefer the mobility in hand-holding a lens. If I manage to get a decent ball head for heavy lens, I would look for the Tamron SP 300mm f/2.8 adaptall-2 lens in the future.

Thanks again,
Hin

Last edited by hinman; 05-13-2009 at 11:15 AM.
05-13-2009, 05:06 PM   #11
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I want to mention about my user errors in using AF.C. Initially I may have thee wrong perception that leads me to think less of the AF.C. Sure enough, I find this description in AF.C from menu, page 106 of K20D menu

QuoteQuote:
AF.C -- Continuous mode --
The subject is kept in focus by continuous
adjustment while the shutter release button
is pressed halfway. Even if the subject is not
in focus, the shutter can be released when
the shutter release button is pressed fully.
When I get lots of bad and blur results in shooting puppies with Pentax DA* 50-135mm f/2.8, it was me making the mistakes in hitting shutter pre-maturely. Also another noted mistakes from me is not paying attention to the shutter speed on moving puppies. I should have bumped up the ISO to make up for the speed. It is the two user mistakes that I need to keep reminding myself.
  • AF.C will allow shutter release even when focus is not confirmed. I need to time the release accordingly
  • Shutter speed need to be watched and maintained in action shot. Bump up ISO accordingly. Use Tv and TAv instead of Av.

Thanks,
Hin

Last edited by hinman; 05-13-2009 at 10:40 PM.
05-13-2009, 06:31 PM   #12
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QuoteOriginally posted by hinman Quote
Daniel, thanks for sharing the tips. I have been using single shot drive mode, I should try your suggestion on firing shots in burst. And if I have the money, I would love to have both the F* 300mm f/4.5 and DA* 300mm f/4.0. I picked the Pentax F* 300mm f/4.5 due to the smaller size and weight and I still prefer the mobility in hand-holding a lens. If I manage to get a decent ball head for heavy lens, I would look for the Tamron SP 300mm f/2.8 adaptall-2 lens in the future.

Thanks again,
Hin
As a birdie shooter you know the frustration/aggravation is proportional to the gratification if you make it.


QuoteOriginally posted by hinman Quote
When I get lots of bad and blur results in shooting puppies with Pentax DA* 50-135mm f/2.8, it was me making the mistakes in hitting shutter pre-maturely. Also another noted mistakes from me is not paying attention to the shutter speed on moving puppies. I should have bumped up the ISO to make up for the speed. It is the two user mistakes that I need to keep reminding myself.
  • AF.C will allow shutter release even when focus is not confirmed. I need to time the release accordingly
  • Shutter speed to to be maintained in action shot. Bump up ISO accordingly. Use Tv and TAv instead of Av.

Thanks,
Hin

Why you did hit the shutter prematurely? You may just fire in burst with your DA*50-135mm and you follow the subject making sure the puppy is in the middle. You will know if you have focused or you have lost focus. High iso say 800 and higher shutter speed do help

Daniel
05-13-2009, 08:55 PM   #13
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QuoteOriginally posted by danielchtong Quote
As a birdie shooter you know the frustration/aggravation is proportional to the gratification if you make it.


Why you did hit the shutter prematurely? You may just fire in burst with your DA*50-135mm and you follow the subject making sure the puppy is in the middle. You will know if you have focused or you have lost focus. High iso say 800 and higher shutter speed do help

Daniel
I will try the burst drive mode as you suggested. Perhaps when the puppies are running towards me, I easily mis-focus when the dog come too close. I don't have the bad pictures to show as I have deleted them to save image storage space.

Thanks again,
Hin
05-13-2009, 09:03 PM   #14
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The Forster's Tern are great birds to shoot. Here are few shots taken in MF while having the AF in auto-select focal points. All are MF and cropped from a distance. SR are off in all shots






first the hovering over water




spotted something
head tilting down




Ready for the dive
about 20 feet above water




I missed the entry




recovery



As much as I like MF on the lens with Pentax F* 300mm f/4.5, I missed quite a lot of shots due to focus errors without the trap-focus, the above are some of the keepers.

Thanks,
Hin

Last edited by hinman; 05-13-2009 at 09:24 PM.
05-13-2009, 10:14 PM   #15
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Beautiful shots guys. Gives me something to shoot for and of course a reason to NEED a faster tele.
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