Headline - DSLRs have imprecise focusing due to their mirrors

Started Apr 5, 2014 | Discussions thread
SteveL54 Senior Member • Posts: 2,696
Re: Perfection is not required

Martin.au wrote:

SteveL54 wrote:

peevee1 wrote:

.... so it is simply impossible to ever calibrate them perfectly for all FLs and distances and apertures even on the high-end bodies which support calibration).

Yup. The calibration required by a separate PDAF sensor is its primary drawback -- but it doesn't have to be perfect.

CDAF by design is looking for focus, no discrepancies matter - what the main sensor eventually sees is what you ultimately get.

Eventually is an interesting word you chose to use describing CDAF. I wonder if CDAF would have eventually focused on this red shouldered hawk diving at me.

It's far from being a perfect shot. (I wasn't very steady tracking this hawk as it dive bombed me. I was wondering if it was going to rake my scalp with its talons.) But it demonstrates what PDAF can do. (Nikon D300 with 70-200mm VR)

And here's another shot from a Canon 20D with 100-400mm.

I like CDAF for its precision, but sometimes there's a need for speed.

Steve

Piece of cake.

The second shot is impressive. Was the bird closing on you? (not hovering)

If CDAF can now reliably aquire and track a small closing bird like that then I will have to reconsider. I'm sure it's just a matter of time for the technology to improve. But then, on-sensor PDAF should do even better.

The DPR review of the E-M5's AF tracking was not very favorable. From page 11 of that review:

"However, despite Olympus' claims about improvements in continuous autofocus and subject tracking capability, we found the system too slow and unpredictable to develop much enthusiasm about. If you're careful about making sure the camera has locked onto a subject, you can expect to get a couple of sharp shots out of a burst but the results are patchy and, for the kinds of 'grab the moment' shooting you'd want it to work for, the results simply aren't reliable enough. The EM-5 is far from unusual in this respect (Continuous AF isn't a strength of contrast-detection AF), but for such an expensive model, and one for which Olympus is pushing the continuous AF capabilities, it's a disappointing result."

I'm not trying to be argumentative, but is the DPR review off and getting these shots is a piece of cake as you say, or did you post a lucky shot?

Steve

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