(Ralf R. Radermacher) wrote in message ...
I've just found out that my new camera (Noblex 150E) is short-sighted by
design. Well, they call it "hyperfocal focussing". We don't even have a
word for this nonsense in German.

In german this method sometimes is called 'Naheinstellung auf
unendlich'.

Now, given that human short-sightedness can be corrected quite
satisfactorily with glasses, is there a possibility of doing the same
with a camera and what would be the effect on the optical performance?

A close-up lens actually shortens the focal length of a given lens. In
your case you obviously have to make the focal length longer (as you
probably can't change the distance between lens and film plane). A
plano-concave or concave-concave lens would do the job. But as with
close-up lens, a poor additional lens will degrade the performance of
the original lens. A single negative lens is not achromatic and not
corrected for astigmatism and other aberrations.

Such lenses are not available as an accessory. Edmund Industrie Optik
makes 'negative achromats' in a wide variety of focal lengths, but of
course these come unmounted. By adding a 'weak' negative lens (i.e.
one with long - negative - focal length) you will get a longer focal
length of the complete system.

Winfried