PDAF Explained..!
Phase
detection auto focus splits the image into two 'copies', then adjusts
the lens elements until the two images 'merge', ie until they're in
phase. Its main advantage is speed.
This differs from contrast detection AF, which phones and mirrorless cameras use. Imagine a black square on a white background on a screen. When it's perfectly in focus, at the edge you will find black pixels immediately next to white pixels - high contrast. If you defocus, you will get a transition from black, through grey, to white - low contrast. The camera adjusts the lens for maximum contrast at edges. These days the CDAF systems in mirrorless cameras are really excellent and are starting to give phase detection a run for its money. They also have other advantages like focus peaking.
This differs from contrast detection AF, which phones and mirrorless cameras use. Imagine a black square on a white background on a screen. When it's perfectly in focus, at the edge you will find black pixels immediately next to white pixels - high contrast. If you defocus, you will get a transition from black, through grey, to white - low contrast. The camera adjusts the lens for maximum contrast at edges. These days the CDAF systems in mirrorless cameras are really excellent and are starting to give phase detection a run for its money. They also have other advantages like focus peaking.
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