No Subject

[jacob@xxxxxxxxxxxxxx (Gabriel Jacob)]

Dr.T writes
>How about the terms "wide", "normal" and "telephoto" used to classify 
>lenses?  These seem arbitrary to me too.  If you view a picture taken 
>with a wide angle lens close enough or one taken with a telephoto from 
>a distance you get a "normal" perceptive.

Hmmm, I am not sure what normal is anymore! ;-)
Once you change the camera to object distance, you won't be able to
get the same perspective at another distance, simply by changing the
focal length. This works for projection/viewers but not for cameras.

>>why pay all this attention to the terms Hypo, Hyper, and Ortho at all? 
>
>Because they are derived from Greek roots?  :-)
>Hypo:  under
>Hyper: over
>Ortho: correct
>Let's see... A subject at 7 feet (2130 mm) is at a convergence angle of
>2* invTan(70/(2*2130)) [70 mm is the lens spacing in the Realist]
>which is 1.9 degrees.  That's a small angle.  My SEM stereopairs are 
>recorded using at least 6 deg. angle tilt.  Yet both appear to have 
>"satisfying depth relationships".  
>George Themelis

Hmmm, all these definintions and mathematics is making me sleepy.
 
Gabriel, going to get some hypno, (i.e. sleep in Greek, like hypnotism)


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