P3D Re: Normal lenses and other myths...

[fj834@xxxxxxxxxxxxxxxxxxxxx (Dr. George A. Themelis)]

>For these thoughts and observations I conclude that the definition of a
>normal lens as matching the diagonal of the image is an arbitrary but
>practical one since we normally view images from distances close to the
>diagonal, which is of course related to our field of view...

Hmmm, I am a bit worried... I have not heard anyone comment on these
speculations so I really don't know if they have any truth in them...

I've heard the following method for finding the "normal" FL in an SLR:  Use
a 35-75 mm zoom, or something similar, and start zooming while looking
through the viewfinder with one eye while having the other eye open.  When
the two images match in size, this is the normal FL.  It seems to me that
this happens when the FL matches some internal distance (from the eyepiece
to the screen where the image is projected?) built (arbitrarily) into the
camera.  Is that correct?

Mike asked about aspect ratio.  Suppose I use my SLR with the "normal" 50
mm lens and then I mask the stereo pair to a Realist format mount.  Does
that mean that my picture now has effectively been recorded with a
longer-than-normal lens since 35 mm is the FL for the Realist size?  But
the relationship between further and distance objects has not really
changed.  Many of us here use full-frame cameras (RBTs, twin SLRs, etc.)
and Realist-format cameras together and mix the images in a projection
show.  What is our "normal" FL then?

-- George Themelis


------------------------------

End of PHOTO-3D Digest 2484
***************************