Monday, March 7, 2005, 4:56:50 PM, John wrote:
JW> Many thanks.
JW> John
OTOH, I did some more reading on the subject, just from web (I can't
dig out my Focal Press encyclopaedia right now, it's not in my home
library sadly), and it seems the formula for loupe magnification is
highly biased... depending on the viewer. The "magnification" is given
as mag vs normal viewing distance of 25cm... Now, the formula I have
given should be 90% valid for comparisons agains magnification given
on loupes. I have even measured the focal length of few loupes I have
at home, at is is roughly valid. However, some places mention the
formula with additional +1 for magnification, so a 50mm lens would be
6x. I think the exact number is not so important, it's just for
reference to loupes that are not specified by focal length but by mag
only. So a 50mm lens would still be comparable to 5-6x loupe, which is
exactly what I found out after viewing countless negatives in the lab
with their 5x nikkor loupe.
Good light!
fra
