[MF3D.FORUM:307] Re: 1/30 voodoo (Oy!)

[Tom Deering <tmd@xxxxxxxxxxx>]

>>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.                ^^^^^

You put you finger right on it.  Yes, it *seems* to be simple, but 
it's not.  Please see my web page for a thorough explanation.  I want 
to be helpful, but others on the list have heard me explain this 
dozens of times.

>But at least 90% of
>my pictures do contain distant objects so the rule is always my 
>starting point.

No.  Considering that MF cameras usually have a 75mm or 80mm lens, 
the 1/30 rule will _never_ be accurate, distant objects or not.

Tom




On 3/25/00, Oleg Vorobyoff wrote:
>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

---
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