In article <4u6elr$btt@cello.hpl.hp.com>, jacobson@cello.hpl.hp.com says...
>In article <4u5nnc$qvc@epervier.cc.umontreal.ca>,
>Melillo Marc wrote:

>>I'd like to have some information about the split view finder that is
>>found in the majority of reflex cameras. More precisely, I'm looking for
>>a ray tracing schematic that would describe the inner working of the
>>split view finder. If you could send a GIF, a WEB adress or a reference,
>>I'd be very thankful to you.

>I can't do any of the things you ask for, but I can tell you how it
>works. The top and bottom of the usual split image device are prisms.
>One selects light only from the left edge of the lens and one from the
>right edge of the lens. (If this seems unintuitive, think of
>backwards rays starting from your eye.) The two images coincide
>exactly when the light coming through the left edge of the lens lands
>in the same place as light coming through the right edge of the lens,
>which is also when the image is in focus.

Nice description, but, uh, what happens when the lens
has field-curvature....;-)
Hope This Helps