How can A6000 beat PDAF, doenst make sense?

Started Feb 12, 2014 | Questions thread
Bart Hickman Veteran Member • Posts: 7,256
Re: No mirror blackout

123Mike wrote:

Bart Hickman wrote:

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

The dedicated sensor may well be able to determine a focus point quicker, but it has to cope with the mirror blackout. If a subject is moving, the SLR must calculate where it thinks the subject will be when the picture gets taken perhaps 0.1s after the last AF measurement was made and then "catch up" once the mirror flips back up to try to reacquire the subject. Predictive AF is usually only available on the higher-end DSLR's.

With the PDAF on the sensor, the camera can continue focusing with no interruptions. No need (or much less need) for predictive AF.

It was only a matter of time before camera processors got fast enough to take advantage of the lack of mirror blackout.


The SLTs have no mirror flap, and besides, the autofocusing on all camera happen before any mirror flap.

SLT's have the same advantage as mirrorless.

AF on DSLRs must stop working when the mirror begins going up.  This is why high-end DSLR's use predictive AF: the servo estimates where the focus should be set based on how fast the subject was moving at the time the mirror went up.

Mirrorless cameras don't need that because the AF sensors can keep making measurements right up until the picture is taken.  They need a little bit of predictive AF because there's some lag between when a focus measurement is taken and the motor responds, but this lag is small compared to the time it takes a mirror to flip up.


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