Very interesting! I try to limit my reliance on AF to objects that
move too fast for me to focus manually, e.g., sports, grandkids and my
paycheck. ;o)
ScottGee1
On 9/28/05, Chuck Norcutt <chucknorcutt@xxxxxxxxxxx> wrote:
> This link <http://www.fredmiranda.com/forum/topic/241524> has some
> extensive discussion on Canon autofocusing and some revealing data on
> the limitations of its accuracy. To quote a piece:
>
> --------------------------------------------------------------
> When the camera determines how far and in what direction the lens must
> move to cancel the phase difference, it does so within a tolerance of
> "within the depth of focus" of lenses slower than f2.8 (down to f5.6) or
> "within 1/3 of the depth of focus" of lenses f2.8 and faster. The depth
> of focus is the range at the sensor plane within which the image of a
> point will be reproduced as a blur smaller than the manufacturer's
> designated "circle of confusion" (CoC). Canon's designated circle of
> confusion is 0.035mm for the 24x36mm format and 0.02mm for the APS-C
> format. The CoC is based on maintaining the appearance of sharpness in a
> 6x9 inch print at about an 10 inch viewing distance (as revealed by the
> Euro-Canon web site). There is no guarantee that images enlarged any
> greater than this will appear sharp.
> --------------------------------------------------------------
>
> Sobering numbers from an autofocus system that is considered very good.
> Buy those KatzEye screens and touch up the focus.
>
> Chuck Norcutt
>
> ScottGee1 wrote:
> > I'd have to dig through my archives to find it, but Popular
> > Photography here in the U.S. published a report about AF focusing
> > accuracy a number of years ago. The results were less than pretty. I
> > wrote Jason Schneider a while back suggesting they run tests on
> > current models, but I wouldn't be surprised if their advertisers
> > raised hell after the first article and Pop is gun shy now.
> >
> > They published 'real life' in camera metering tests a couple of times
> > with similarly ugly results and we haven't seen one of those recently
> > either.
> >
> > FWIW/ScottGee1
>
>
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