Roger Wesson wrote:
(Snip) For an object at a given distance to be in focus on the film,
the lens must be in one unique position (ignoring depth of field). But
for that object to be in focus on your retina, when you look through
the
viewfinder, the situation is different - if your eye normally focusses
short of your retina (ie you're shortsighted), then what you see
through
the viewfinder will focus perfectly on your retina if the camera lens
is focussing slightly longer than it should do, and vice versa. So the
image on your retina is in focus, but the image on film will not be.
(Snip)
======================================================================
I don't think that's right. AFAIK, your eye has to focus on the image
formed on a ground glass screen. This is normally at an optical
distance of about 2 metres (I think) from the eye. People with optical
defects may not be able to focus on the ground glass screen at that
distance, so they need a dioptric correction lens. The best way to set
a variable dipotric lens is to rototate until the engravings on the
focussing screen are clear, *without* a lens attached to the camera!
Regards,
=====
Ray
"The trouble with resisting temptation is
you never know when you'll get another chance!"
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