How can A6000 beat PDAF, doenst make sense?

Started Feb 12, 2014 | Questions thread
viking79 Forum Pro • Posts: 14,147
Re: How can A6000 beat PDAF, doenst make sense?

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?

Even some dedicate CDAF cameras are faster than some PDAF cameras.  There is no hard rule saying PDAF is better than CDAF.

Historically, CDAF has been slower as it takes video from the sensor, does some image processing on it, and determines where it is sharper.  Better algorithms might take too much power or require more powerful processors to perform the calculations in real time (fast enough that the processor has some idle time).

Some huge limitations are how quickly you can read out data from the sensor, how quickly you can detect edges in that data, etc.  Now with faster sensors that can refresh the video at say 120 times or 240 times a second instead of 30 times a second, lens motors designed to step through a range of values very rapidly and precisely, software calibrated to the lens that can analyze the image to see how defocused a lens is, etc, and CDAF has become very fast.

CDAF has some weak points, like low light means it has to integrate the video longer to get strong enough edges to detect, etc.  So this quickly it can step through the focus range, etc.


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