In article <19970218180400.NAA29924@ladder01.news.aol.com>, edleica@aol.com says...

>A camera focusing screen is neither at infinity or at 40cm (16 in)nominal
>reading distance but is instead at approximately 1m. Most people can
>focus adaquetly with their distance prescription until at least their late
>forties. When you go to your optician/optometrist/ ophthalmologist ask
>him /her to help you with this special need. I have found through my
>experiance as an optician the best vision through the camera is found by
>holding trial lenses over the eyepiece lookinf at the focusing screen
>without a lens on the camera. Look at the finder info (shutter speed and
>aperature if they are clear remount the lens and focus again this should
>be the correct power for an eyepiece lens.

This is good advice, until one reaches the end... (the finder info
is often at a different apparent distance than the focusing screen).
With the lens off (and a matte-centered screen), the correction that
gives the sharpest view of the GG "grain" should be best... BTW, I
had the camera-focus eye distance-lens set for that correction, and
the two (25mm flat-top, placed lower-than-normal) bi-focals set for
two other distances, giving me sharp focus from near to infinity
without the gaps in focus that I had experienced before - and it
optimized camera manual-focus ability.
Hope This Helps