Why Mirrorless cameras and Micro 4/3rds, in particular, are important to me.

Started Apr 21, 2013 | Discussions thread
sgoldswo
sgoldswo Veteran Member • Posts: 5,717
Re: Continuous AF

Chris R-UK wrote:

sgoldswo wrote:

Chris R-UK wrote:

sgoldswo wrote:

[snip]

Sure - but if you are talking about M43s it is only tracking that might not be up to a pro level DSLR. Single shot AF is generally faster to autofocus. If you bring the GH3 into the equation it might not stand up to a D300 or D7000 level APS-C camera in tracking or continuous autofocus, but it will give other APS-C DSLRs a run for their money even in tracking.

I own both a Canon 7D and a GH2 and I like both, but I am also realistic about the limitations of PDAF.  I have done a lot of experimentation with the GH2's AF-C system for birds in flight and it is unusable.  All the M4/3 birds in flight photographers that I know use single shot AF.

An extract from the GH3 review on this forum:

"The tracking system, can be a little reluctant to lock-on to a subject (such that we doubt it will achieve a lock in time to catch most fast-occuring events). Once locked the camera will attempt to re-focus with the subject but the results we got were pretty hit-and-miss, with the camera frequently refocusing onto the background or not keeping-up with the subject."

This is no better than the GH2 and all other mirrorless cameras.  So far only the hybrid Nikon 1 Series has solved the problem of continuous PDAF focusing.

I'll be honest, while I don't shoot BIF, I've had much better results with the GH3 than previous M43s cameras in tracking mode. It's possible to lock on a person or a car etc and get decent focus tracking, even on objects heading directly towards you. Certainly up to entry level DSLR tracking and better than Sony's implementation in their DSLT line.

The problem is that PDAF cameras can't consistently maintain focus on a fast moving object.  As the review says, the GH3 frequently refocuses on the background.  If it does that with a fast moving target you have lost the shot.  By the time that you have picked up focus again the target is gone.

If the camera can't maintain focus on a fast moving target at least 80% of the time (and I suspect that an entry level DSLR or any Sony SLT can do that, my 7D is nearer 95%) it is too unreliable to use for any fast action photography.  Better to use AF-S which is reasonably reliable for single shots and give up shooting in bursts.

I don't think the gh3 can manage 95% but you might want to give a GH3 a go for tracking  performance. I think you would find it a lot better than your GH2 (bear in mind it uses AF running twice as fast as the CDAF in the GH2 and has a much faster processor). I certainly don't think your 80% threshold is out if the question.

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