Focus adjustment, help!

Started Jun 5, 2012 | Discussions thread
Roland Karlsson
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Re: Initial conditions...
In reply to SRT201, Jun 6, 2012

SRT201 wrote:

The output of a control system is based on input and initial conditions and it's accuracy is also limited by internal resolution, noise, etc.

An AF system is a complex control system and the final "focus point" will be affected by the initial conditions especially considering the size of the Pentax AF points. That makes it all the more difficult to accurately test the Pentax AF system. I would think a secondary focus target would have to be setup such that it can be dropped into the optical path allowing the camera to focus on a point that is not the test chart but is fairly consistently located relative to the test chart. Each focus test would be started by moving focus back to the initial point first and then removing the secondary target. That would allow one to test AF accuracy and repeatability from a known point every time.

Its my experience that the K-5 focusses somewhat too close and then move the lens until it gets a lock. That would probably lead to the camera focussing on the closest point it can lock at.

This also would mean that if the camera moved the lens slightly slower it would lock on a closer point.

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