Milan Zahorcak
[..]
> I use a Nikon F3HP and wear glasses. I am both near-sighted and have
> astigmatism in my 'shooting' eye. The High-Point finder makes focusing
> while wearing my glasses easier, but I am puzzled, and have several
> questions about is actually going on.
[most deleted....]
K.K. and AE1R. had some excellent things to say on the subject...
I solved the problem another way, which also solved a vision problem
and allowed me to avoid tri-focals. Look on my web page under "I babble",
then "Four-Way Glasses" for a description of my solution... Good luck!
Hope This Helps
David Ruether - http://www.fcinet.com/ruether
I'm glad you asked this question, because it has been one of my pet peeves
that camera manufacturers in general ignore the fact that a lot of their
customers can't focus very well at 1 meter (39.4 inches). When your
optometrist checks your vision, he uses a target which is at 20 feet. If you
need glasses, he will prescribe the correction necessary for that distance.
It would seem to make sense, therefore, for camera manufacturers to design
their viewfinders to have an apparent distance of 20 feet between the
eyepiece and the focusing screen. However, it is an almost universal practice
among modern camera manufacturers to set that apparent distance (called
"virtual image distance") to 1 meter.
Younger people have no problem accommodating to the 1 meter distance; but as
one ages, the range of distances over which the eye can accommodate shrinks,
rendering critical focus at 1 meter almost impossible. This is the reason why
a lot of older photographers switch to auto-focus, believing that their
difficulty in manually focusing their SLRs is an indication that their
eyesight is failing when all they need is the proper eyepiece correction
lens. The addition of a +0.5 diopter lens will make the focusing screen
appear to be at about 6.5 feet, and the addition of a +1 diopter will yield
an apparent distance of infinity. The ideal power, of course, would be + 0.8
diopter which would make the screen appear to be at 20 feet, but these
correction lenses are usually only available in 0.5 diopter increments.
In your case, your astigmatism is presumably already corrected by your
glasses, so you
should wear them when using your camera in combination with one of the
correction lenses offered as accessories for your camera. It's a good idea to
bring your camera to the store with you when you purchase the accessory
lens. You will want to check performance with a +0.5 and with a +1 diopter
accessory to see which you prefer. Since you have the F3, you should also
know that the F3 accessory lenses are labelled with the combined power in
diopters. For example, the +1 diopter lens for the F3 is labelled "zero".
Karl Aimo ae1repair@aol