Ian -- actually, you have it, that's all the same process. I am
extremely nearsighted (-10.50 diopters in one eye, -9.50 in the other).
my father was mildly far-sighted, +1.50/+2.25. what the diopter
adjustment on your bins does is exactly what you thought, it adjusts the
(usually right) barrel relative to the left, to correct for the slight
differences we all have (even with correction with glasses or contacts)
between our eyes. & for some of us, this is not entirely stable, but
may vary by a 1/4 or 1/2 diopter from day to day. so that adjustment
essentially changes the magnification of the right barrel -- if you use
8X bins, the right barrel is slightly more or less than 8X, depending on
your eyes.
hope this helps. jck
ICTerid wrote:
I hesitate to open up this can of worms on the Listserv (and I hope
that one of our fellow subscribers just happens to be an optometrist
that can answer this in one fell swoop), but does anyone know what
the diopter adjustment on our bins ACTUALLY does???
1-We know for a fact that most of our optics have it, and that using
it usually improves the performance of whatever brand/model we own.
2-Most go from L to R (minus degrees L, to plus degrees of
change R- or vice versa, but only in rare cases).
My first impression was that it basically compensated for the
inherent difference in prescription strength that is normally present
between one's left and right eye- simple enough, right?
Until my father found a site on our wonderful www (while in search of
a simple answer to a seemingly simple question) that, though pertaining
to dual-eyepiece microscopes (just bins for amoebas, at least in my
eyes), said that the minus and plus ranges on a diopter
adjustment-wheel ONLY pertained to degrees of nearsightedness and
farsightedness, respectively.
This left me more boggled than ever... and raised the question of NS
versus FS being related to one's own vision rating (20/20, etc).
After a 4 hour debate with my father + the questioning of every
nearsighted and farsighted birder I know, I've gotten no closer to the
answer of this simple question: What does our friendly diopter ACTUALLY
do??
Any insight is welcomed, though off the Listserv might be more
prudent...
Ian C. Topolsky
Hamilton, VA
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