Thanks again, time to build myself a loupe I think. John
---------- Original Message ----------- From: Frantisek <[EMAIL PROTECTED]> To: John Whittingham <[email protected]> Sent: Tue, 8 Mar 2005 01:49:20 +0100 Subject: Re: M 4/200mm vs F 4-5.6/70-210mm at 200mm > 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 ------- End of Original Message -------
