On 5/29/12 at 10:04 PM, (Howard Jones) wrote:
So I now can have 2 500 mm lenses on the same camera but with completely different results depending on which one I use.
if this is really true then somebody badly miss-labeled one (or both) of your "500mm" lenses.
focal length is a physical property independent of sensor size. the confusion arises because most lenses were built for a specific film size, so people automatically assume the focal length is what defines the field of view (or angle, or magnification factor), while in fact it's the combination of focal length and image size (so for the same focal length and sensor size, you get the same field of view - assuming the lens image circle covers the full sensor and you manage to focus both properly).
lots and lots of this has been written about this, if you're interested in the backgrounds a good place to start is probably the wiki (or any physics book on optics)
http://en.wikipedia.org/wiki/Focal_length http://en.wikipedia.org/wiki/Lens_(optics) ++ chris _______________________________________________ Nuke-users mailing list [email protected], http://forums.thefoundry.co.uk/ http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
