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Autofocus Technical Discussion
#1

There's a great series by Roger Cicala from Lensrentals - basically he does some empirical tests to see how consistent and accurate the various focusing methods are, and also how equipment plays a part. He goes into the theory and also has the hard data to back up his claims so it's very fascinating reading.

It was interesting to see that in general - phase detect autofocus (basically what all DSLRs use by default) is fast to lock, especially when tracking moving objects. But compared to contrast detect (used by most compacts, mirrorless cameras and also when using LiveView on DSLRs) appears to offer the most accurate focus consistently.

In the latter part of the series he looks at Canon lenses and bodies, and notes that the newer bodies and lenses all have seen great improvements in their AF - in particular the 5D Mark III and 1Dx have phase detect accuracy and consistency that rivals contrast detect. Sadly though, my 3/4 year old 7D appears to be one of the worst in terms of consistency.


Anyway do have a read - very worthwhile:
- Part 1: http://www.lensrentals.com/blog/2012/07/...t-accuracy

- Part 2: http://www.lensrentals.com/blog/2012/07/...old-vs-new

- Part 3a: http://www.lensrentals.com/blog/2012/07/...non-lenses

- Part 3b: http://www.lensrentals.com/blog/2012/08/...on-cameras

I do hope he covers Nikon as well, as it would be interesting to see how their AF system stacks up and whether they experience the same issues.
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#2

Just wondering if anyone read this? I posted it just before the outage so it may have slipped by... anyway I thought it was a worthwhile read..
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#3

Hey looks like Roger has delivered the long awaited follow up on Nikon AF performance. Unfortunately (or maybe fortunately for us here) it's only limited to Full Frame cameras, and not APS-C sensor bodies.

http://www.lensrentals.com/blog/2012/09/...full-frame

His key summary points:

Quote:- The Nikon full-frame cameras all do well with center-point, single-shot AF.
- The newer bodies seem a bit better than the older ones.
- There don’t seem to be dramatic changes with a few camera-lens combinations like the newer Canon bodies and lenses showed.

Also, it's interesting to note that just like their Canon counterparts, phase detect AF is less accurate than contrast detect (by the same margin) and newer lenses and newer bodies exhibit more accurate focusing.
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