Re: [photo-3d] Pulfrich pseudo & history & web refs

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

Absolutely!  Pseudoscopy is just as prevalent in Pulfrich images as in any
other form of stereoscopy.   This can be proven when a scene is such that
all of the action is continually moving in the same lateral direction, such
as an image of a subject on a turntable.  Reversing the dark filter
left-for-right (holding the filter in front of the other eye) will produce
an obvious pseudoscopic impression.

Many people do not recognize pseudoscopic images, especially if there are
strong monoscopic depth cues present, and/or if their attention is focused
on a small part of the action that might be stereoscopic or flat while the
rest of the image is pseudoscopic.

JR

----- Original Message -----
From: "Abram Klooswyk" <abram.klooswyk@xxxxxx>
To: "PHOTO-3D" <photo-3d@xxxxxxxxxxx>
Sent: Tuesday, October 31, 2000 1:10 AM
Subject: [photo-3d] Pulfrich pseudo & history & web refs


> Mark Dottle 29 Oct 2000:  (...)
> >.... and of course there is no "pseudo" effect experienced.
>
> In fact there _can_ a pseudoscopic effect!
>
> I have written on "A PULFRICH 3-D HISTORY" in Stereo World
> jan/feb
> 1989 vol 15 No 6 pp 14,15,27. A few excerpts:
> >>
> As early as 1965 W.C.Dalgoutte, the famous editor of the
> British
> Stereoscopic Society Bulletin, wrote on the 3-D effects in
> ordinary TV
> programs when watching them with a filter before ONE eye - an
> effect
> comparable to the old chrono stereo effect which displaces
> moving
> objects when the single views of a stereo pair are made
> sequentially.
> Dalgoutte used a pair of polarizing filters and rotated them
> one
> across the other until a substantial loss of light was
> achieved.
> (...)
> Tokyo Movie Shinsha Company made "Remi", a "Three-Dimensional
> Animation" series in color of no less than 51 episodes of 30
> minutes
> each. Movements where designed to give a Pulfrich 3-D effect
> when a
> filter was placed over the left eye. The story was based on
> the famous
> international children's classic "Nobody's Boy", written in
> 1878 by
> Hector Malot. This series was broadcast in Japan in 1978. It
> seems
> that some 10 million "Pulfrich glasses" with a neutral grey
> filter on
> the left and a clear acetate on the right were distributed in
> Japan
> for that series.
> (...)
> ....the only country in Europe where it was broadcast seems to
> have
> been the Netherlands. The episodes were on Dutch TV screens
> twice a
> week from October 1979 to well in the year 1980. The Pulfrich
> glasses
> were supplied from Japan, and were distributed free with
> "Prodent", a
> toothpaste brand. About a million glasses were made for the
> Netherlands, which covered almost all Dutch children of the
> appropriate age group. (...)
>
> The story is appropriate to a lot of moving scenes, for the
> boy Remi
> is a supposed orphan traveling through France with a group of
> entertainers. Generally about one third of an episode showed
> the 3-D
> effect, for obviously not all movie scenes could have
> horizontal
> movements.
>
>   As John Dennis reported on the Nuoptix demonstration (Stereo
> World
> Sept./Oct. 1988, p.2) movements in the opposite direction
> cause
> pseudoscopic disturbances. This was especially the case when
> the
> traveling group was visible moving through the landscape,
> apparently
> followed by the camera. Although closer than the background,
> they
> moved to the RIGHT, which displaced them farther back than the
> background. This effect was fairly evident to me, but as John
> Dennis
> correctly supposes, few in the general public seem to notice
> pseudoscopy before you ask  them, and even then some never get
> the
> point.  <<
>
> Sofar for the quotes. There is a lot on the Pulfrich effect on
> the
> net nowadays.
> Gabriel Jacob 29 Oct 2000:
> >Actually the easiest way to demonstrate the pulfrich effect is right
> >there in your hand! Just move your mouse!
>
> But on my system the cursor moves somewhat jerky... :-)
> Check out some java demonstrations. Swinging pendulum in java
> at:
> http://www.bu.edu/smec/lite/perception/pulfrich/exp.html
> and Mark Newbold's java applet at:
> http://dogfeathers.com/java/pulfrich.html
>
> A still of a classical pendulum demonstration apparatus is at:
>
http://jedlik.phy.bme.hu/~hartlein/physics.umd.edu/deptinfo/facilities/lecde
m/o2-11.htm
>
> (Of course even now we don't always have to look at computer
> screens,
> hanging a real object at a real string 2 or 3 feet long still
> can be
> done :-))
> In the Pulfrich effect there are at least 3 variables:
> "pendulum"
> speed, filter density and viewing distance. All three affect
> experienced depth.
>
> To go deeper in the subject check the "Pulfrich Homepage":
> http://www.siu.edu/pulfrich/index.html
> There you find several original papers, including Christianson
> &
> Hofstetter's "Some Historical Notes on Carl Pulfrich" and even
> Pulfrich's original 1922 papers (in German, PDF of
> photocopies).
>
> Abram Klooswyk
>
>
>
>