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

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

My friend Tom writes:

>We obviously are not communicating.

I guess we are not :-)  

>The page in question, http://www.deering.org/basis.html, says "how to
>calculate optimal separation of two cameras."  The 1:30 rule is nowhere
>near "optimal" for macros, as the picture clearly shows.

Please define "optimal separation".  Is this the separation that
results in 1.2 mm OFD?  If this is the case, who says that 1.2 mm 
on-film deviation is the optimum for a stereo image?  Just point me 
to the source.  This is the root of our apparent miscommunication.  
If you convice me that 1.2 mm is OPTIMUM and not MAXIMUM then I will 
say that you are correct.  

>...the 1:30 rule is "close enough", until you shoot close-ups.  Then 
>it falls apart.  It predicts a number that is nowhere near the correct 
>answer to the question "what is too close to the camera" or, "what is 
>too far apart."

Please define what do you mean by "correct answer".  The 1/30 rule does 
not claim to predict the MAXIMUM or any kind of OPTIMUM.  It claims to 
produce a decent stereo pair that is easy to view.  If it does what it 
claims then it works.

I am not playing a game with words here.  Some beginners might really
think that 1.2 mm on-film deviation is some kind of optimum and go
for that.  Well, I have news for them:  It is not!  For me personally,
1.2 mm OFD in a close-up is a bit too much.  And I have mentioned that 
I have seen PSA winners with near zero OFD.  And many people have 
recorded stereo pairs with more than 1.2 mm OFD and they have survived 
(the audience too!)

I cannot make myslef any more clear than that.  If you have some 
explanations regarding the definitions of "optimum" and "correct", 
I am eagerly waiting to hear them...  Otherwise please advise your 
audience that the graphs in your web site calculate the separation
of two cameras for the "generally accepted" MAXIMUM 1.2 mm OFD and
change the wording of your statements to reflect that the 1/30 rule
fails the predict the MAXIMUM.  Also (this is optional :-)) you can put 
a disclaimer to the effect that "maximum" does not mean "optimum" and 
that many stereo photographers have produced award-winning stereo 
photographs with OFD much less than 1.2 mm.  The graphs that you show
are limits not to exceed, not a goal to aim.

-- George Themelis


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