Loved your prose, B Sent from my iPhone > On Dec 4, 2016, at 1:55 PM, Bob W-PDML <[email protected]> wrote: > > >> On 4 Dec 2016, at 21:51, Larry Colen <[email protected]> wrote: >> >> Igor PDML-StR wrote: >>> >>> Larry, >>> >>> I haven't done much of astro-photography, so, I am just >>> curious: why focusing at infinity wouldn't work in this case >>> (i.e. turning the focusing ring to the end of the range)? >>> Is it just because the particular lens(es) are not designed or >>> manufactured well for infinity focus? (E.g. they have "beyond infinity" >>> focus at the end of the wring range.) >> >> Exactly. I've been told that "to infinity and beyond" is necessary for >> autofocus, although that doesn't seem true for my FA77. I suspect that it's >> just a lot less expensive to guarantee that a camera will focus past >> infinity than to carefully calibrate to go exactly to infinity. I wonder >> how much sample variation there is in registration distance between the >> mount and the sensor, as that would also affect the "infinity focus point". > > Owing to the curvature of spacetime it should be possible with that lens to > photograph the back of your own head. > > But you'll probably have to wait until the day before yesterday to do it. > > B > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions.
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