Frozen image info from Herbert McKay

[P3D Michael Kersenbrock <michaelk@xxxxxxxxxxxxxxxxxx>]

Greetings, 

	Happen to run across this subject in U.S Camera Magazine 
last night.  Seemed appropriate to one of the current sub-threads.  
Contains a minor "twist" to things not yet mentioned.

Mike K.

...................................................................


		STEREO Photography  (Column)
		   By Herbert C. McKay
		U.S. Camera, March 1953, Page 10

Q. I recently made a shot of a horse jumping a' hurdle.  The animal,
  "frozen" in midair, looks artificial in stereo.  How can this be avoided?
			 -L. M. W., Des Moines.

A. 

   Your problem is highly interesting because in a planar shot this frozen
appearance would denote complete stopping of motion and would indicate a
successful picture.  The very fact that it is not satisfactory to you in
stereo shows the highly realistic quality of stereo.  We can accept the
planar shot because it is only a picture, but in stereo the mind rebels at
the defiance of gravity in what we know to be a wholly impossible manner.
   As to the remedy, that is still a point of argument among stereo
photographers.  One of the basic technical requirements of stereo is that of
the greatest possible definition, which means that all motion must be
completely stopped.  Yet there are many competent stereo photographers who
insist that a certain degree of blur-of-motion is a distinct advantage in
eliminating the effect to which you object. This has been most often brought
up in regard to water; particularly breaking waves.  In this type of subject
the complete stopping of motion gives the water a hard, crystalline
appearance which of course is not at all a faithful reproduction of the
original.
   The matter is of course related to certain inherent deficiencies of human
vision.  We do not have the power of instantaneous vision.  Anything we see
is an image extended over a considerable period of time.  This time is on
the order of one-tenth of one second. If anything moves through any
appreciable space during that time we actually see a blurred image.  This
continued extension of vision (persistence of vision) is the thing which
enables us to see a continuous image when a movie film is projected as
alternating periods of a picture and a dark screen.
   We seem to see a sharp image, and to some extent this is caused by our
ability to "follow" the moving object with our eyes and so reduce the degree
of motion with reference to our eyes. But unless the object is moving at a
relatively low speed, this following is not perfect and there is some blur.
   Therefore, although we are seldom conscious of this visual blur of
motion, a stereo picture which does exhibit a slight degree of this blur is
often more realistic and more satisfactory than one in which the moving
object meets the orthodox requirement of being absolutely sharp.  The degree
of blur permitted to remain and your technique for obtaining just this exact
degree of blur is a matter of individual judgment and individual technique.
It is noticeable, however, that the amount of blur which is acceptable is
less than that often used to indicate motion in a planar photograph.


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End of PHOTO-3D Digest 2254
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