[MF3D.FORUM:305] Re: 1/30 voodoo

["Oleg Vorobyoff" <olegv@xxxxxxxxxxxxx>]

Tom Deering wrote:
>
>The 1/30 "rule" is sophistry masquerading as fact. You may as well use dice.
>


I don’t know.  The 1/30 rule seems to be an expression of a simple geometrical
relationship.  If that is not factual, what is?  The rule tells me precisely
where the stereo window will appear once a picture taken with 35mm lenses and
containing faraway objects is properly mounted.  So with a stereo pair taken at
70mm spacing the window will appear at 70mm x 30, or about 7 feet.  The rule
applies to other lenses and formats proportionally.  So a 1/15 rule would apply
with a 17mm lens on my Canon or a 35mm lens on my Pentax 6x7.  Likewise, a 1/60
rule would apply to a 70mm lens on the Canon or a 135mm lens on the Pentax.

The 1/30 rule need not apply if there are no faraway objects, since the picture
may be mounted with a nearer object at apparent infinity.  But at least 90% of
my pictures do contain distant objects so the rule is always my starting point.
If the scene can tolerate some window violation or, conversely, needs some
breathing room behind the window, I use the rule to move the ultimate window
back or forward accordingly.  No sophistry - just previsualizing the final
mounted picture, like I presume any good stereographer would.

If I’ve got it wrong, please set me straight.

Oleg Vorobyoff