P3D On the "why the 1/30 rule does not work"

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

I just had a chance to look at Tom's site.  I was curious to see why 
he says the 1/30 rule does not work.  I did not download the 
spreadsheet but was able to understand what is going on.

At some point Tom sites an example and writes: "The camera separation 
should be 4 inches maximum. Notice the 1:30 rule, shown as a dotted 
red line, would have predicted a 1 inch separation, way off."

"Should be"?  "Way off"?  What is going on here?????????

Then he writes: "These tables assume a 50mm lens, and a maximum  on-film 
deviation of 1.2, based on the formula published by John Berkovitz. "

The name is "Bercovitz" and the key word is *maximum*.  Maximum means
"it should not be any larger than that".  It does not mean "optimum".
The 1/30 rule ALWAYS gives less than 1.2 mm.  SO, IT WORKS.

Sorry folks, but you need to read Tony Alderson's message on this
subject.  It was kinda long but right on the money.  Anything from
-1.2 mm to +1.2 mm on-film deviation will work (outside these limits
might cause eyestrain in projection but can also work in a viewer).
No one can claim that +1.2 mm is the optimum.  It is just a limit
not to exceed.  If I want to use the 1/30 rule, I will always be under
this limit.  So 1/30 will ALWAYS work for me.

This is the math.  The rest is personal preferences.

Will all due respect,

George Themelis


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