just got 7d, I am really frustrated right now.

Started Aug 27, 2012 | Discussions thread
mmullen Veteran Member • Posts: 4,285
Re: just got 7d, I am really frustrated right now.

WilbaW wrote:

Sorry - you are citing the very article that I clearly said was misguided.

Please describe a test that proves your claim, and explain how the results of the tests described in the article lead to different conclusions.

The tests in the article are misguided because they jump to conclusions that are not supported by the test results.

I have long held that Canon DSLR's AF procedure starts out in closed loop mode and, as the phases of the two ends of the AF detector approach alignment, the AF system reaches a point at which it has enough data to determine where to stop the lens. At that point the system becomes open loop because it moves the focus position one final time without 'looking' to verify satisfactory alignment. Most of the tests in the article prove the first part of my hypothesis but do nothing to disprove the second part of my hypothesis.

In fact, one test in the article appears to prove the second part of my hypothesis (that the last AF command to the lens is open loop. That test is titled "The Open-loop Final Step Test". But the article treats this test as if it a special case (even though my interpretation is consistent with the results of all of the other suggested tests in the article.

I do not claim to have any further proof of my hypothesis (that the final AF step is open loop) but I called the article misguided because none of the tests prove that the last step is closed loop (and one of them appears to show the opposite).

In my opinion, that is jumping to a conclusion without any facts to back it up.

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Mike Mullen

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