Winsor Crosby wrote:
> Wrong triangle, I think. Hard to explain in just text. And you
> changed what I said a little bit. Did not say anything about a center
> subject at 10 feet.
>
> A different way to think about it. Use a protractor and draw a 10 cm
> semicircle. Now draw a straight line tangent to the semicircle at the
> 90 degree point in the middle of the arc. Assume that you want your
> center of sharp focus at 45 degrees on the circle. Now when you
> reframe so your subject is to the side your 10 cm focus setting is
> still on the semi circle. But you have a straight line that
> represents the plane of focus and your subject you focused on is in
> front of it.
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OK, I see the point and I agree if we're talking macro distances and
large angles from the optical center (assuming the optical plane is flat
which is a big asusmption). And I see how DOF saves us at more typical
distances and angles. Guess I'll turn the multiple autofocus points
back on during macro focusing. Ooops! I misspoke. I mean I'll turn on
the single "correct" autofocus point that best corresponds with the
subject's position.
Chuck Norcutt
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