Micro Focus Adjustment Revisited

Started Mar 27, 2013 | Discussions thread
Jerry-astro Forum Pro • Posts: 10,134
Re: Yup... better method IMHO

tonyjr wrote:

I found a flat thing like a poster was fine at up to 10 feet . Go out to 20 feet and you need an angled object - It is a DOF thing . A lens can be front focused and the front leg of a chair still be in focus while rear is not .

If that works for you, hey, more power to you.  I have found that using the largest possible aperture, regardless of distance, seems to work just fine with a flat target.  You need to test at various MFA settings and pick the one that either gives the sharpest image or is centered between the two that just begin to show front and back focus.  The problem with angled targets, particularly at a distance, is getting the camera to precisely focus on the exact target point.  Canon's experts have said as much publicly as well.

BTW, if you really like angled targets, the method used by LenAlign is a nice combination of both techniques.  The target itself is perpendicular and straight, however, right next to it (and in the field of view) is an angled ruler.  That gives the camera a reliable focus target and you the ability to see the focus alignment over a range of distances.

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