What is the best m43 for focus tracking?

Started Mar 31, 2013 | Questions thread
tomsailor
Junior MemberPosts: 36Gear list
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clarification of "focus tracking"
In reply to clengman, Apr 1, 2013

clengman wrote:

JamieTux wrote:

Hey everyone, since selling my Canon gear to move to m43 I've been shooting with just one top quality body (I have a gf2 as well buits really lacking in dr for my style of shooting so one useful camera only scares me!) I had the money put aside to get the new improved AF all singing all dancing Oly when its announced but all seems quiet on that front at the moment.  So I'd like to get a complementary camera to go with my om-d.  If that is the top at the moment then I guess I will need to hire where needed until the new one is announced and make a decision then.

I've even been looking at the GH3 despite its size, but I can't find anyone willing to put their neck on the line and call a winner!

Thanks in advance for your thoughts!

I see the discussions of "focus tracking" a lot and I wonder when this is actually useful. As Mick, Anders and axlotl pointed out there's a big difference between C-AF (which seems to be very good in all the newer m43 cameras), and C-AF with tracking.

To take the commonly cited examples; sports, kids playing, and flying birds, why is the tracking part really useful? Why would you want to keep the camera absolutely still and rely on the camera to follow the subject. Seems to me that it's preferable to track the subject by panning the camera. As long as you can keep the AF box on your subject, an E-M5 (or even an E-PL3 or G3 and all subsequent cameras from what I understand) should do just fine in C-AF mode at keeping whatever is in the focus box in focus.

C-AF with tracking seems like a separate issue. Whether it's a CDAF or PDAF camera it still requires some sophisticated software dedicated to object recognition. (i.e. determining that a particular patch of light projected on the sensor represents a discrete, permanent object and then following it even as it's color, luminance, shape and size change.) This is more a machine vision problem and not a focusing problem. Are there really any cameras that are good at that?

You make very good point here, but people use confusing language which in the ends leads to half truth wisdom circling the internet.

Focus tracking is when the subject is moving around the area of your viewfinder, the camera needs to hand the subject from one focus point to the next one without loosing it; -> tracking. There is not necessesarily focusing involved in this operation. Focus Tracking is a different thing from continuous autofocus (C-AF).

C-AF means the camera is adjusting focus as the distance between the subject and the camera changes. Preferably this is done while you keep the subject at the same focus point all the time. There is no focus tracking here. You are panning with the camera to keep the subject at the same place relative to the area of your viewfinder.

A sophisticated PDAF system is pretty good with C-AF as it can measure the movement and therefore use some predictive element in C-AF and move the lens element in the right direction. Works great with a high-end DSLR, but not so good with a consumer DSLR and needs good lenses with highly responsive (USM)focusing motors.

CDAF systems, as used in m43, do not measure the movement but are checking constantly in C-AF mode if the subject is still in focus by moving the focus elements forwards and backwards to confirm or adjust focus. The USM motors in DSLR lenses are not good for this, that's why you need other tchnologies, e.g. STM. Current m43 cameras and current lenses are the fastest out there for this technique.

C-AF with m43 does not work as good as C-AF on a high-end DSLR but is on par with consumer DSLRs (G5, GH3, OMD, GH2 probably also). My first impression from the GH3 is that it is the best one, using the f2.8 lenses (the new firmware update for other Panasonic lenses should improve this to the same level). The cameras without a good EVF do not work at all from my experience, as the lag of the displays on the back of the camera is too big to keep the subject properly on the selected focus point while shooting in burst mode.

Combining C-AF with focus tracking cannot be recommended so far. It simply requires to many focus iterations and processing power to work at the moment. But it is just a question of time as processing power can be improved with each camera generation. And video is leading the way...

As m43 has the fastest autofocus (focus acquisition this is) and the more precise one compared to DSLRs, it gives good results if you adapt your shooting technique. Applying what you learned and perfected with your DSLR will not give you the best results with m43. Moving up the learning curve, I regard the OMD, GH3 and G5 as "fit for the job", although there are use cases where the high-end DSLR machine gun will always give better results.

Regards

Tom

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