Re: Effects of lens length

[P3D Marvin Jones <72657.3276@xxxxxxxxxxxxxx>]

> question - if you did this, would you have the same stereo image
> as if you had shot both sides with lenses of the same FL? That is-
> if you crop an image taken with a 50 mm lens to the same part as
> an image taken with a 80 mm lens, and make them the same size - would
> you have the same thing as two pictures both taken with 80 mm lenses?
> 
No. The length of a lens impacts the relationship of foreground and background
objects. There is a famous shot in the movie Jaws (which has been copied by many
others since) in which the camera started on a shot of Roy Scheider at a fairly
wide-angle setting of a zoom lens. As he realized that the shark was attacking,
the camera was pulled away from him quickly, and the lens zoomed in toward him
at the same rate. The result was that the actor appeared not to change, but the
background seemed to rush up toward him. As the lens became longer, in effect,
the relationship between the foreground object (the actor) and the background
appeared to compress, and the effect was heightened by the camera movement and
the zoom counteracting each other to give the appearance that the actor did not
move. I'd guess this effect would seriously harm the stereo effect in the
hypothetical situation you suggest.


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