Validating the Optical Formula - The optical formula I have used is one of the foundation principles of modern optical technology
and science, so in that respect it can be considered uncontestable. The fact that it is included in a professional manual for Hollywood
Cinematographers, who's very livelihood depends on the information being correct, lends further credence to the validity of the formula.
The
formula states that knowing three numbers, you can solve for the forth. But in the spirit of testing even our base assumptions, I
have tested the formula in a circumstance where I do know the four numbers, and put the same three in, to see if the formula verifies
the forth. So with a filming I have done, I have put in the lens focal length, the subject height on film, and the measured distance
from subject to camera, to see if this does indeed calculate the height of the subject in life being photographed.
Testing the
Lens Formula:
The above, for both 15mm and 25mm lens, is theory. In a film test, I chose to verify it with an actual filming
test, using a Kodak K-100 camera and each of the lenses, filming a man known to be 6' 2" tall, in shoes, and at a measured distance
of 102' from the camera. The 102' distance was specifically chosen for illustrative purposes because in Chris Murphy's fine books
on the PG Film, one diagram specifically estimates the distance from Roger's camera to the film subject as being 102' for Frame 352.