So how does Pentax AF work (BF on DA21)?

Started Nov 17, 2006 | Discussions thread
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Laurens Senior Member • Posts: 1,391
So how does Pentax AF work (BF on DA21)?

My DA21 on an istDS also has BF problems. Most of my other lenses are OK, apart from the DA40. Other ppl (volosong) have also tested the DA21 on numerous bodies and have shown that the problem is with the lens.

Most ppl claim that the AF system is open loop (with confirmation), which I am inclined to believe. From one of the Pentax patents the amount of defocus as measured by the AF system is converted into a pulse count by the CPU and sent to the lens/motor.

Do the lenses have any data stored for pulses/focal distance? How are the lenses calibrated? Are they calibrated?

Laurens

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