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Archive 2012 · 5DIII/1DX Servo AF: "recipes" and a simple model
  
 
PetKal
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p.1 #1 · p.1 #1 · 5DIII/1DX Servo AF: "recipes" and a simple model


This simplified approach to Servo AF parameter setting is intended for folks who are struggling with the manual like I am, and who are keen on getting the drift of their new cameras' Servo AF performance fast and easy, while experts are not likely to find anything new here.

First of all, let me say that I believe that one should explore and evaluate a piece of gear on the type of target which represents their general photography interest as closely as possible. For example, if you like shooting antique porcelain dolls, then by all means test your gear on dolls.

Since I like to photograph birds here and there, it only makes sense that I'd test my new lenses and cameras on birds. However, therein resides a problem of test target availability. Even when available, no two bird flights are alike, the weather and light changes all the time, and a number of flights photographed may not allow sufficiently high confidence level in the results.

Canon have provisioned their 5DMkIII and 1DX user's manuals with six AF tracking "recipes" which are motion type based, and they are meant to help users select the most appropriate recipe for their tracking application, by selecting a recipe which comes close to the application. The recipes consist of different combinations of three tracking parameters: sensitivity, acceleration/deceleration and AF Pt. switching speed.
For brevity's sake, let us refer to them as A,B,C. In addition, users can custom assign different values to each of A, B and C.

Well, those recipes I found a bit confusing, thus I "dismembered" them by starting to look at A, B and C on their own. The ambiguity and overlapping of recipes is thereby reduced to a simplified question: given my particular tracking application, what should A, B and C be set to ? Now we come to the verification stage, or test shooting if you will. The issue is not only how well our 1st iteration of A,B and C settings work, but one should also do a bit of sensitivity analysis by permutating, say, A only, and observe the impact of it on tracking effectiveness.
Clearly, that approach can get a bit difficult with test targets such as non-captive birds.

There is one easy way of helping the test process: instead of chasing moving targets outdoors, we can use a moving lens on a fixed target at home.
A plastic action figure on my desk becomes my test target. A painting placed behind the target becomes my "busy" background. I shoot the target with a lens 135-200mm FL, and the target head should cover about 10-15% of the VF area.

Now let us try to do one little experiment with the setting A (tracking sensitivity):
Select centre AF point with 9 AF pt. expansion and, obviously, the camera should be in Servo AF mode.

(1) Dial Setting A to (-2)
Focus on the target (e.g. a plastic figurine). Move/play the lens over the target in any direction, back and forth, in such a way that all of the AF pts (including the expansion ones) clear the target periodically. Observe the AF behaviour, such as how long it takes for AF to jump from the target to the background.

(2) Dial Setting A to (+2)
Repeat the same process as above.

The net effect of the above test will be a fair difference in the observed AF tenacity or "stickiness".
In addition, you can have the lens fixed on the target, and then you pass an object quickly in front of the target and observe the resistance of AF to getting derailed from the target, again, as a function of different Setting A values.

There are similar ways in which a target movement can be simulated in order to get a better feel for the effect of permutations in B and C settings as well.

There you have it, lottsa writing here although the approach outlined is really very straightforward. Not perfect by any means, as one should always do real life testing as well, but the exercise described has helped me get a better feel for the new AF system.



Aug 14, 2012 at 08:28 PM
svassh
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p.1 #2 · p.1 #2 · 5DIII/1DX Servo AF: "recipes" and a simple model


Nice writeup, thanks for the tips. I've been considering how to get a better grasp myself. My youngest is getting sick of getting out of the pool to take a running jump back in so Daddy can play with his camera.


Aug 14, 2012 at 09:01 PM
Gust
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p.1 #3 · p.1 #3 · 5DIII/1DX Servo AF: "recipes" and a simple model


Peter thanks for his info.
I like your posts

A: the first dial setting is a big difference in the speed of the AF reaction.
B: cannot see here any difference in the behaviour of the AF.
C: reacts perfect when you use zone [ and all the AF points]
the AF becomes very quick , now testing with the 400II [ is now on his way for firmware]



Aug 15, 2012 at 08:37 AM
DocsPics
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p.1 #4 · p.1 #4 · 5DIII/1DX Servo AF: "recipes" and a simple model


tag (Thanks Peter)


Aug 15, 2012 at 09:12 AM
 

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Gust
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p.1 #5 · p.1 #5 · 5DIII/1DX Servo AF: "recipes" and a simple model


What I noticed is the behaviour is different if you move the AF point out of the centre.
tried that with 61, only cross and 15 points.



Aug 15, 2012 at 09:27 AM
PetKal
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p.1 #6 · p.1 #6 · 5DIII/1DX Servo AF: "recipes" and a simple model


Gust wrote:
What I noticed is the behaviour is different if you move the AF point out of the centre.
tried that with 61, only cross and 15 points.


Thank you, Gust, I haven't done anything yet with the off centre AF points, but I will try to confirm your findings. Also, will send you a note about accel/decel tracking simulation later on today.



Aug 15, 2012 at 10:26 AM
Gust
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p.1 #7 · p.1 #7 · 5DIII/1DX Servo AF: "recipes" and a simple model





Aug 15, 2012 at 10:36 AM





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