P3D cherished ways

[Tom Deering <tmd@xxxxxxxxxxx>]

Abram Klooswyk wrote:
>I'm sorry to interfere in the debate, but "It assumes
>a focal length of 35mm or so" seems a conceptual error.
>I know (from the Archives) that the statement has been
>made before on Photo-3d, when base calculations were
>an issue, and that Tom Deering probably only repeats
>what other scholars have said.

As anyone who visits my web site can abundantly see, I have worked 
out the geometry for myself.  Of course, my work is built on the work 
of others.  The fact the other scholars say the same thing as me is 
awfully gratifying.  I am particularly grateful for the kind words of 
John Bercovitz, whose name is  synonymous with stereo math.

But I am most thankful for the comments from beginners who are 
looking for a better way.  These people have noticed that some of 
their photos did not turn out as they expected, even though they 
followed an often-repeated "rule".  These beginners need to know 
there is an alternative.

Some old-timers hate to see their cherished ways discredited.  If you 
are new to this, try both ways and see the difference.  Then the 
choice is yours to make.

Stereo photography is inherently an exercise in applied geometry. 
The concepts that your stereo camera is built upon, from the spacing 
of it's lenses to the the arrangement of its built-in "stereo 
window", are fundamentally geometry in action.  The better you 
understand it, the more you can control it.

Cordially,

Tom Deering
http://www.deering.org/curves.html


>If you are a beginner trying to sort out this issue, try
>this simple example:
>
>Set your Realist on a tripod over a bed of flowers.  Tilt the camera
>down so that nothing is farther than 10 feet away, and nothing closer
>than 4 feet.
>
>Four feet?  (You mean, not seven feet, like the 1/30 "rule" says?)
>That's right, here is a common example where the "rule" is way, way
>off.  Set the focus of your camera to 6 feet, and the diaphragm to
>F16, and take yourself a handsome stereo photo. Nice and clear, with
>good depth.
>
>When you get this photo back, you will have learned something that
>Mr. Themelis doesn't know: in lots of cases, the 1/30 "rule" is
>*flat* wrong.