At 16:38 1/20/01, Mickey Trageser wrote:
So, there's no direct relationship between the angle of view and focal
length? Does this have to do with whether or not there is rectilinear
correction?
-Mickey
The "angle of view" typically given for a lens is across the diagonal of
the film frame. It is based on the focal length and the size of the film
frame when the lens is focused at infinity. This is why the angle of view
of an 80mm lens is wider on a medium format camera than a 35mm camera.
For a rectilinear lens, it can be found by simple trigonometry: forming a
triangle with the base as the film diagonal and its height as the focal
length. The angle at the two legs at the apex is the angle of view. If
you want the "horizontal" or "vertical" AOV, change the length of the
triangle base to the size of the appropriate side of the film frame. The
angles of view in Hans' eSIF files for the Zuiko's are all across the 35mm
film frame diagonal. This is important to remember if when doing certain
types of photography . . . e.g. sometimems architectural or photometric . .
. when one can need a specific angle of view for a specific subject size
and distance from the camera lens.
The mathematics for a fisheye angle of view are different.
-- John
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