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04-12-2016, 06:18 AM   #16
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For birding, practically, I always try and use centre focus points. I've had lots of times where I locked focus in the centre, then switched to an off-centre point for compositional reasons, then couldn't lock focus, and had to switch back. My current solution is centre point only, use my K-3 and crop. I only use an expanded grid for tracking. And it's not often I do that.

04-12-2016, 09:32 AM   #17
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QuoteOriginally posted by Rupert Quote
I see now....you guys are tracking moving objects.
For me:
AF-C with AF Hold and center point Expanded Area AF for action
AF-S with center point for still shots, i.e. focus and recompose

I use Hyper-Program or TAv for stills shooting. I have User1 configured for action. To switch from shooting a bird in a tree to BIF, I just need to turn the Mode dial two clicks. AF-C is not good for still subjects.
04-12-2016, 09:54 AM   #18
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QuoteOriginally posted by noelpolar Quote
I often wonder with longer lenses if a little bit of field curvature is an issue on bird shots when one uses the centre point to focus on an eye and then reframes significantly away from the eye to take the shot
The Angry Photographer was talking about this on YouTube not that long ago - essentially if you have a narrow DOF and you recompose, you risk shifting the vital focus point out of the true plane of sharp focus when you recompose.
04-12-2016, 11:35 AM   #19
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QuoteOriginally posted by a5m Quote
Also I believe certain AF Points (IIRC the 3 in the center: The main one in the middle, the one above it and the one below it) are more sensitive than the rest. For example in low light situations the center 3 will be more sensitive and therefore better at locking focus.

I found this on the Ricoh Japan site that gives a clearer explanation:



High-precision AF with F2.8 luminance flux linear sensors

The center sensor and two sensors just above and below it are designed to detect the luminance flux of an F2.8 lens for high-precision autofocusing. When using a very fast lens with a shallow depth of field, these sensors greatly improve the focusing accuracy.

Dependable AF at super-low minimum luminance of –3 EV

The K-3’s high-sensitivity AF sensor assures dependable autofocus operation down to a minimum luminance of –3 EV (when using 25 middle sensors), preventing the AF mechanism from slowing down or being confused by high-contrast areas in back-lit situations. It also captures low-contrast subjects with great accuracy.
http://www.ricoh-imaging.co.jp/english/products/k-3/feature/img/bod_img_02_02.jpg
Are the two vertical "sticks" also autofocus points?

Randy

04-12-2016, 11:41 AM   #20
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QuoteOriginally posted by audiobomber Quote
AF-C is not good for still subjects.
It's simply unusable on a K-30. I have mine set to focus priority, but I have no idea what my camera thought was in focus in the picture below. Between the camera switching focus from the fence boards to either the front or back of the water bowl to one of the not perfectly still birds, I think the camera just gave up after 5 minutes of hunting and released the shutter out of frustration.

04-12-2016, 12:52 PM   #21
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QuoteOriginally posted by RGlasel Quote
It's simply unusable on a K-30. I have mine set to focus priority, but I have no idea what my camera thought was in focus in the picture below. Between the camera switching focus from the fence boards to either the front or back of the water bowl to one of the not perfectly still birds, I think the camera just gave up after 5 minutes of hunting and released the shutter out of frustration.
Sounds like you were using Auto AF point selection? AF-C with center point AF would work better, but still not nearly as reliable as AF-S and single point.
04-12-2016, 02:31 PM   #22
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QuoteOriginally posted by audiobomber Quote
If you are not using Expanded Area AF and AF Hold in AF-C mode, you are completely subverting the camera's ability to track. The K-3 and K-3 II have sophisticated tracking algorithms based on an "86,000-pixel RGB light-metering sensor for extra-accurate detection of the subject’s shape and color". Without these features you may as well be using a K-5 or K-7.

Here are my current recommendations for BIF with a K-3:
TAv mode:
- Set aperture for sharpest MTF - f/5.6 with the DA*300, f/8 if you're also using the TC. Shoot at f/8 with 55-300mm, do not use a TC. If you're shooting in dim conditions, the DA*300 is acceptable wide open, even with the TC. The 55-300 is unacceptably soft wide open.
- Shutter speed according to conditions. I find 1/1000s works most of the time. Never go below 1/500s. Don't be afraid to push ISO. Noise is correctable, motion blur is not
AF-C, Hi-Speed continuous burst:
Center AF point, with 25 point expansion
Center-weighted metering, add 0.5EV compensation, fine tune in p-p
Shake reduction off

Custom Menu Parameter Settings:
16. 1st frame action in AF-C - Focus priority (make sure focus is on the target before shooting, or you'll have a string of misses)
17. Action in AF-C Continuous - Focus Priority
18. Hold AF status - Medium, bump up to High if required. IME, AF Low allows focus to drift to the background too readily.

Read more at: https://www.pentaxforums.com/forums/38-photographic-technique/317498-birds-fl...#ixzz45bs8GE68
Thanks for this highly detailed post.

I realize that I am presently only using a small part of what the K3 AF system has to offer, and the reason is that I am slowly getting acquainted with its basics.
I can't even get 50% of my shots (stationary) in perfect focus yet. I thin it's getting better because the first 200 shots were a total mess.
Sure enough, there will be soon time when I will "have to use" something other than spot AF.
What I did though is to copy/paste this post of yours in a Word DOC for reference. I'm sure this will come in handy very soon when the marshes and small lakes unthaw. (still darn too cols here still at this time of the year .... Mother Nature not cooperating much at all in 2016! )

And I am also revisiting the back AF button, something I had neglected for quite some time along with this fine thread about "perfect focus every time" .

Thanks for the link as well.
You will hear from me when I start using this method of tracking.

Cheers!

---------- Post added 04-12-16 at 05:34 PM ----------

QuoteOriginally posted by noelpolar Quote
I often wonder with longer lenses if a little bit of field curvature is an issue on bird shots when one uses the centre point to focus on an eye and then reframes significantly away from the eye to take the shot..... especially near wide open apertures at closer shooting distances.
I have no expertise on the subject, as you may well have found out from me posting this thread, but you have a good point here: personally, I have yet to consistently getting a "great" shot using spot AF AND recompose (with the DA*300/4).
04-12-2016, 04:33 PM   #23
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QuoteOriginally posted by jpzk Quote
I have yet to consistently getting a "great" shot using spot AF AND recompose (with the DA*300/4).
I have to think something else is wrong. Are you sure your camera and lens are calibrated? I use AF-S, CF&R all the time with the K-3 and DA*300 on stationary birds and rarely miss. The biggest difference I notice with the K-3 vs. previous Pentax bodies is the tiny center AF point, which allows me to pinpoint the bird among the branches and leaves.

04-12-2016, 05:50 PM   #24
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QuoteOriginally posted by audiobomber Quote
I have to think something else is wrong. Are you sure your camera and lens are calibrated? I use AF-S, CF&R all the time with the K-3 and DA*300 on stationary birds and rarely miss. The biggest difference I notice with the K-3 vs. previous Pentax bodies is the tiny center AF point, which allows me to pinpoint the bird among the branches and leaves.
You might have just hit the sore point of my "dilemma" and before trying all sorts of different AF methods, I'd better check for BF/FF.
Well, I did, sort of: not your accurately devised testing with fancy charts but one I took from a couple of links:

1. Method used by a member of this forum here:
https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/89665-focus-focu...us-charts.html
2. With that (AF- telephoto chart) chart:
https://drive.google.com/file/d/0B_44neE8iNsXUzRQSEpjRnpoYUU/view

How good is that for checking FF/BF ... ? Not quite sure.
I did some early "tests" outside on various targets and it seemed "ok", but you and others might see something I am not seeing, thanks to my perfectly/ elliptically/astigmatism formed left ocular globe which is my dominant eye !
So I ended up playing with the fine adjustments and then decided to reset everything back to factory defaults!

The first "target" tests are here:
https://www.flickr.com/gp/rdlphotos/9LB194
The real world "birds" shots that were satisfactory are here:
https://flic.kr/s/aHskxP46z6
And finally, some high ISO tests, trying NR methods:
https://www.flickr.com/gp/rdlphotos/7a8NR6

After that, not much in terms of "testing" and/or trying to calibrate this gear.
As I mentioned earlier, I get few keepers so far.

Let me know if the links work ... I'll try something else if they don't.

Thanks for the time reading and helping.

JP

Edit: I had forgotten to say that all of those images were taken using spot AF and at factory defaults for the AF.
04-13-2016, 03:38 PM - 1 Like   #25
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The weather looks like it will be cooperating this weekend and hopefully I will be able to take some shots outside.
I saw my first large flock of Snow Geese a few minutes ago !
Great time to see how I do with this AF thing.
05-01-2016, 07:39 PM   #26
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So, I am back to report a few things I have tried over the past several days:

Using AF-S on stationary subjects :
TAv, spot metering, spot AF.
1. As long as the bird (my subject) doesn't move, I am getting better "keeper rate" at roughly 50%. Not great though.
2. As long as the contrast is high, the subject will more often be in focus. With subjects "blending" with the background, the results are atrocious.
3. Definitely doing better at f5.6-8.0 although I thought that this K3 would at least behave better at f4.0-5.0. (like it did with the K5).
4. For BIF in AF-S ... as long as the subject is (very)distant AND with high contrast, it is OK. When the subject is closer and I have to pan ... forget it!
I will post some pics that I have taken today to show what mess this caused. A couple of harriers chasing one another at reasonable distance and this was with great weather: dry, sunny. The pics look OK uncropped but they sure are "soft" when viewed at 50% cropping. I will try to post those tomorrow.
Again, I used to be able to get along quite well with the K5 (and DA*300/4) for BIF shots ... not anymore; this camera is giving me a headache!
So, this means that I have to follow the advice of audiobomber and start using the AF-C mode.
I've tried this in the past with the K5 but because the results were so poor, I totally ignored this feature for the K3.

On the other hand, when eventually I nail the focus, the images are extremely detailed and vibrant !
So, back tomorrow with some pics.

Cheers!
05-01-2016, 09:08 PM   #27
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QuoteOriginally posted by jpzk Quote
4. For BIF in AF-S ... as long as the subject is (very)distant AND with high contrast, it is OK. When the subject is closer and I have to pan ... forget it!

It's what AF-C is for, Jpzk, otherwise you've just focused for where the bird used to be!
05-02-2016, 10:02 AM   #28
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QuoteOriginally posted by clackers Quote
It's what AF-C is for, Jpzk, otherwise you've just focused for where the bird used to be!
That could be it !

On the other hand, as I mentioned a few times earlier, it still puzzles me that I "could" get some very decent BIF shots with the K5 using the AF-S while now it is quite an ordeal with the K3.
So .... AF-C it will be for BIF.
((Bad weather again here today ... 5 Celcius and rainy with a nice "fresh" Northeast wind!! ... so that'll have to wait until next weekend. ))
05-05-2016, 01:40 PM   #29
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Alright ... I've just set up a User mode for BIF and now I am wondering (besides the other settings) :
If I normally use the shutter button for AF-S and decide to use the back button for AF-C, will this be saved in the User mode?
Will I then be able to switch back to the previous settings with the AF button (shutter) still "there" ?

e.g.:
User 1 .... AF-S with shutter button for AF
User 2 .... AF-C with back button for AF.

Thanks !!
05-05-2016, 02:02 PM   #30
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I don't see why back button focus will be useful. Its main purpose is a quick change from AF-S to AF-C. With the User mode set for AF-C, there's no need to switch back and forth with anything but the Mode dial.

I have a severe bias against BBF. It's unnatural for me. I've been using half-press for focus for many years. Now that I can switch from AF-C to AF-S on the mode dial, BBF has lost its advantage and kept its disadvantages.
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