Re: A Bit More About the New Big White Lenses That Are Coming
With DPAF the STM focus algorithm would be like; move forward 22 steps fast, move forward 1 step slow.
A usm lens algorithm could be like; move forward half the distance, check focus, if front focused, move forward half of remainder, if back focused, move back half the distance. Repeat above. keep repeating until in focus. When the lens is slow or the focusing sensor is having a hard time, this hunting is apparent to user.
Kit. said:And how is it different from the AF protocol EOS camera uses with any other EF lens?nchoh said:A stepper motor is controlled very differently than other types of motors. A stepper motor has steps, hence the name. Each step is a fixed angle. For example a stepper motor with 365 steps would move precisely 1 degree for each step called and move forward or backward a precise amount based on the screw. So the difference between a stepper motor performance versus other types of motors is because the stepper motor is able to take different instructions.
With DPAF the STM focus algorithm would be like; move forward 22 steps fast, move forward 1 step slow.
A usm lens algorithm could be like; move forward half the distance, check focus, if front focused, move forward half of remainder, if back focused, move back half the distance. Repeat above. keep repeating until in focus. When the lens is slow or the focusing sensor is having a hard time, this hunting is apparent to user.
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