Robert McClure
22-Jan-2007, 07:15
Hello!
I have two quick questions related to the following lens currently up for bid on E-bay:
http://cgi.ebay.com/FUJINON-W-300mm-f-5-6-in-COPAL-SHUTTER-327483_W0QQitemZ270081786059QQihZ017QQcategoryZ15248QQrdZ1QQcmdZViewItem
First, considering this lens will stop down to f90, and if image circle is 420mm at f22, can I actually calculate what circle would be at f32, f45, f64, and f90. Will it cover 7x17 at stops smaller than f22, say at f64? Short of actually testing, can I draw any conclusions?
Second, I notice that more often than not, image circles are generally cited at f22. Is this because at smaller stops it often becomes doubtful that a lens will continue to perform acceptably? I mean, in the case of the above lens, should I expect that usable image circle beyond f22 will continue to increase and that for contacts even f90will be adequate?
Must I test or is there info out there (Sandy King, etc.)?
Thanks in advance!!
Robert McClure
I have two quick questions related to the following lens currently up for bid on E-bay:
http://cgi.ebay.com/FUJINON-W-300mm-f-5-6-in-COPAL-SHUTTER-327483_W0QQitemZ270081786059QQihZ017QQcategoryZ15248QQrdZ1QQcmdZViewItem
First, considering this lens will stop down to f90, and if image circle is 420mm at f22, can I actually calculate what circle would be at f32, f45, f64, and f90. Will it cover 7x17 at stops smaller than f22, say at f64? Short of actually testing, can I draw any conclusions?
Second, I notice that more often than not, image circles are generally cited at f22. Is this because at smaller stops it often becomes doubtful that a lens will continue to perform acceptably? I mean, in the case of the above lens, should I expect that usable image circle beyond f22 will continue to increase and that for contacts even f90will be adequate?
Must I test or is there info out there (Sandy King, etc.)?
Thanks in advance!!
Robert McClure