Re: Pulfrich Take 2 (resend)

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Fri, 13 Jun 1997 12:25:28 -0500
>From: P3D Scott Langill  <slangill@xxxxxxxxx>
>Subject: Pulfrich Take 2

I think you have put a lot of thought and effort into this issue and into
this post. I agree with some of your statements, partially agree with some,
and strongly disagree with some. I believe that discussion of these issues
serves a useful purpose in improving the depiction of 3D.

As a general comment, in cases where I disagree with your statements, it
is often not that I think you're entirely wrong, but that you sometimes
appear to include the assumptions that what you perceive when you view
the various systems is what *everybody* perceives, and that the relative
valuation you place on the impact of imperfections in the various systems
is a standard that should be shared by everybody.

>This is not the
>case with the Pulfrich Effect except under extremely controlled
>circumstances where the constraints placed on a filmmaker or
>videographer arguably would totally disrupt the storytelling function. 

I agree that it's a problem, but the use of the word "totally" 
comes across as hyperbole.

>As to Pulfrich being the only game in town, I would refer you to the
>article in the April 1974 edition of American Cinematographer entitled
>"The Video West, Inc. Three Dimensional Photographic System". The still
>photographs made with their technique accompanying the article are
>clearly viewable in 2D without glasses and in 3D with glasses. The
>technique was designed for video and film. 

What exactly is this technique?
And if it's so great, how come it's still so little known after 23 years?

>The issue is whether you can tell an effective story or present an
>effective story with all the constraints that compensating for the
>misrepresentational effects of movement with the Pulfrich Effect. I
>doubt whether they are aiming for an accurate representation of depth, I
>think "a jazzy effect, with occasional pronounced depth effects" sounds
>more Hollywood probable to me.

You raise an interesting point. For the recent anaglyph and Pulfrich
broadcasts, my personal view was that they both played the stereo for
"jazzy effects", but that the anaglyph stereo was pushed "beyond the
breaking point" (the point at which the constraints are violated and the
stereo fails), while the Pulfrich broadcast was not. Extending beyond
these two methods and the recent broadcasts, I don't think I've encountered
any 3D show where the 3D was not used for "jazzy effect" - it seems to be
an almost irresistible temptation. Perhaps over time the makers of shows
will learn to stop hyping it up so much, in the way that they eventually
learned to stop hyping color movies/television (as compared to black and 
white).

>> ...is it possible that you are "Pulfrich blind"?...

>I find the ad hominem attack a little disingenuous. 

I didn't intend that as an ad hominem attack. If you're going to offer
your perceptions of these techniques as the standard by which we should all
live, then it's not out of place for us to ask what perceptual characteristics
you might have. 

>Pretty neat, but are these accurate
>portrayals of the objects. No. A funhouse mirror is entertaining, but
>should I promote it as how things really look?

You seem to indicate in several places that anaglyph broadcast *is*
accurate portrayal of depth. But doesn't that depend on specific spacing
of the cameras in filming it, the size of the TV screen, and your distance
from the screen? The Pulfrich depth perception of a scene can be
inaccurate (even with straight tracking of a motionless scene), but so
can anaglyph, if all of the factors mentioned above aren't just right.
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You made no mention of the calculations that would have had to be
performed to figure out just how far to sit from the TV set to get an
accurate portrayal of depth with the anaglyph broadcasts, and I don't think
the network made any statements on that issue either.

If you're referring to the fact that the depth is inconsistent in a Pulfrich
program where there is extraneous motion, then that's really a non-issue
since I don't think anyone here supports the opposing view. It's true
that Pulfrich broadcasts do not usually follow the constraints to get "proper
stereo", but that's not inherent to Pulfrich - just to the way it's usually
used. Anaglyph is also in practice usually not used to produce "proper stereo".

John R


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