Occasionally, I see mentioned in a post that someone is
having to turn to an AF camera system due to eyesight
changes. As we age, our ability to focus our eyes
diminishes, and first bifocals, then trifocals
become necessary to be able to see at varying
distances. I mentioned in a post some time ago
that I was thinking of trying another solution -
a solution, which, if it worked, would also optimize
my vision for being able to continue to use the 35mm
SLR camera ground glass viewing screen for focusing
(I have never liked AF, or those miserable "focusing
aids" that clutter the centers of some viewing screens).
Having gotten around to having an unusual pair of glasses
made (the loss of ability to focus with a Nikon F2, followed
by the 6006 and N90, and most recently, the FA/FE/FM [the
8008 and F3 continued to be OK, but more difficult to
use than previously], prompted me to try), I am
happy to report that the new glasses work well,
with a bit of a reservation. First, I will describe
what my situation is: I am nearsighted in both eyes,
and unable to focus over a wide range, even with
bifocals. I am unwilling to turn to trifocals
(the line of the bifocal bothers me, so I do not
want to add another - and I need a larger lens area
for camera viewing than the middle lens of a trifocal
would provide [I found lineless lenses totally useless,
since the sharp viewing angle in both the distance and
close parts is VERY restricted, and I like wide-angle
vision]). My current glasses have large lenses, with
25mm flat-top bifocal insets set unusually low to
keep them out of the way while using a camera.
The main lenses are set for good distance vision,
and the bifocals are both set for about two feet (I
can see well at about one foot without glasses).
This provides good wide-field distance vision
(including a good view of the ground), and
good near-field vision, but the area between
about six feet and two and one half feet is not
sharp - nor is the area closer than about one and
one half feet (the camera viewfinder screen apparent
distance must be about four feet, and I just miss it
with these glasses). My new glasses have the right
distance-lens set for optimum infinity sharpness,
the left (camera focusing eye) has +.5 diopter
added to bring the optimum distance to about
three and one half feet, the right bifocal is
set for about 22 inches, and the left bifocal is
set for about 17 inches. This provides a continuous
range of sharp focus from infinity to about 15 inches.
I can now see all Nikon viewing screens VERY sharply,
which makes manual focusing easy and reliable
(astigmatism, and having many camera bodies,
discouraged me from placing corrective lenses
in each camera eyepiece). I can now also see well
(after a short period of adjustment to a bit of
monocular vision) under all conditions except
low-light. For that, I have ordered glasses
with .25 diopter less under-correction
for the left eye, with everything
else remaining the same (it should
be possible to focus a camera, though
not so easily, and low-light distance vision
should improve). I was hoping to get away with
one pair of glasses for all purposes, but it
didn't work out that way, alas (unless
the pair on order is better
for mid-distances than
I think it will be).
Hope This Helps