Hey all, quick question about focal lengths.
I've researched this and while I've found many technical details of focal length and angle of view and all that, I haven't found a definitive definition of what the millimeters in the focal length is actually a measurement of.
-Is it the exact mm measurement between a certain part of the lens elements and the focal plane (sensor/film)? Is it the measurement of any obvious thing viewable by your own eyes relating to the camera/lens/subject??
Does it have to do with converging/diverging of light? It must be a measurement of something obvious and simple right?
Obviously, these focal lengths in mm are very very short distances (e.g. 50mm equals just about only 2 inches).
So what is it?!
EDIT: I got this from Wiki, but I still don't understand exactly what the measurement is:
"A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the pencil of rays more strongly, bringing them to a focus in a shorter distance."