Re: Pulfrich - direction?, Anaglyph - red where?, and Stereo

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Mon, 9 Jun 1997
>From: P3D  Adam L. Beckerman inquires:
>.................
>***Pulfrich questions:***
>...................
>Does Pulfrich have a greater effect when objects (or the camera) are =
>moving in a certain direction?  (Mention has been made about motion to =
>the left (or is it right?) and the ER shot being counter-clockwise when =
>viewed from above)?

*****  The Pulfrich effect is totally motion dependent. The delay effect
caused by the darkened lens will create an effect with motion from any
direction. It is only the horizontal directions that are of interest to
stereoscopic matters. The particular motion of interest is relative motion,
something moving at a different rate than surrounding subject matter. You
can experiment with any pair of sunglasses with one lens held in front of
one eye. Try it in front of each eye and notice which motions create a
*normal* spatial displacement. For standard TV shows there is motion in all
directions and ample opportunity to use the lens over both eyes.

The commercial use of Pulfrich seems based on glasses that are worn in only
one position. That being the case, the producers have to arrange that all
relative motions are in the same apparent direction. In fact that is only
half the stereo Pulfrich equation. *REAL* Pulfrich glasses would be more
like LCS glasses, with the dark side switched automatically according to the
predominant direction of motion in the scenes.

The simplest method to play with the effect is to wear a dark lens over one
eye and watch your mouse cursor as you sweep it back and forth across the
computer screen at different rates of speed.

>
>***Anaglyph questions:***
>.................... He says to view the images with the red on =
>the left.  However, I see greater depth when the glasses are Red right.  =
>Is this correct?  I thought I should view it properly with red left =
>since the red filter is 'eliminating' the right image and only allowing =
>the left eye to see the left image.  Why do I see greater depth with red =
>right?

*****  There is no known physiological reason why one side would be better
or more effective than the other, other than in specific cases where some
rare eye condition might influence the situation. Red on the left is the
most often used *standard*. You can compile your images in the reverse order
and use the glasses with red on the right and see which you like best. I
doubt that you will actually see a difference in perceivable depth. If you
are switching the glasses but not the image, then you are viewing in
pseudoscopic mode, where objects appear inside out. That may create an
impression of either greater or lesser depth depending on your level of
awareness.

>
>***Stereo Camera/Viewing media questions:***
>.... So, I'd like to buy my =
>_FIRST_ stereo camera.  My primary goal is to get one cheap and easy!!  =
>This being my first stereo camera purchase, I'm mainly interested in =
>getting good effects with very little effort/expense, and build up from =
>there.........................

*****  Cheap and easy? - Get two identical cameas and tape or otherwise
fasten them to some common base material so they can be carefully aligned
and stay that way. Then with experimentation you can practice snapping both
shutters at the same instant. In California you're not likely to find stereo
cameras in thrift shops or flea markets! Some folk on this list might be
selling such cameras and that would be recommended, if it's within your budget. 

>
>Since I'm fairly new to all of this, would I buy normal print film and =
>just be using up twice as many rolls as I normally would (since the =
>number of pix on a roll is essentially halved)?  

****  Yes, about twice the film! Prints or slides depending on your viewing
methods. I use mostly prints and scan them for computer viewing, or freeview
the prints. If you can find a slide viewier, you may want to use slides.


>....Finally, is there some =
>other cheap, quick, and easy medium I should consider for viewing them =
>(e.g. slides -- w/o special projectors, screens, etc.)?  I have an old =
>Viewmaster from my not-so-long-ago youth that could be of use?  I know =
>there has been much discussion of whether print or slide viewing is =
>better, but even though I may be sacrificing some quality, I just want a =
>viewing medium that is (again) quick, cheap, and easy.
>..............

****  There is no easier or cheaper method than freeviewing (by cross-eyed
method) side by side prints. It's worth learning for that reason alone, even
if you predominantly use other methods. There is a device called the
Freeviewers assistant which comes in a choice of handmade wood, or a fold-up
cardboard form. It takes the work out of freeviewing and is very convenient.
Keep exploring any methods you get a chance to try and eventually you will
settle on one or more methods that work best for you.

If you are considering stereo in your computer, consider getting one of the
LCS systems as this is very much more enjoyable than anaglyphic methods.

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/
http://3dzine.simplenet.com/


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