07-24-2012, 03:41 AM
Hi Wim:
[quote name='wim' timestamp='1342782199' post='19485']
With PDAF, the camera doesn't actually try to focus at all, that's just the theory. It tries to calculate a best match for the amount of lens extension or focus element movements (stepper motor increments) required for the lens to focus correctly based on the starting position of the lens. Furthermore, there is no active feedback loop with PDAF, although focus hunting in difficult cases comes fairly close.
[/quote]
But from various resources I read that the PDAF process in reality works in an iteration way. For example http://graphics.stanford.edu/courses/cs1...cusPD.html, which in the "The autofocusing process" section states that "In practice it usually moves close to the correct position, then takes additional measurements to refine this position". So, I assume that after the lens takes reaction to the command of the camera, the camera does check if the lens has followed its command correctly (otherwise there would be no the "green dot" (or beep) confirmation I think). Could you clarify this?
Thanks,
Frank
[quote name='wim' timestamp='1342782199' post='19485']
With PDAF, the camera doesn't actually try to focus at all, that's just the theory. It tries to calculate a best match for the amount of lens extension or focus element movements (stepper motor increments) required for the lens to focus correctly based on the starting position of the lens. Furthermore, there is no active feedback loop with PDAF, although focus hunting in difficult cases comes fairly close.
[/quote]
But from various resources I read that the PDAF process in reality works in an iteration way. For example http://graphics.stanford.edu/courses/cs1...cusPD.html, which in the "The autofocusing process" section states that "In practice it usually moves close to the correct position, then takes additional measurements to refine this position". So, I assume that after the lens takes reaction to the command of the camera, the camera does check if the lens has followed its command correctly (otherwise there would be no the "green dot" (or beep) confirmation I think). Could you clarify this?
Thanks,
Frank