Re: [photo-3d] RE: Digital Video 3D

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

----- Original Message -----
From: "Marcus Warrington" <marcusw@xxxxxxxxx>
To: "Photo-3D" <photo-3d@xxxxxxxxxxxxxxx>
Sent: Friday, March 16, 2001 2:39 AM
Subject: [photo-3d] RE: Digital Video 3D


> Some one said that a problem with the NuView is that it creates only
> Field-Sequential encoded videos. True, but if you then capture this to
> a digital stream for non-linear editing you can then extract these two
> streams and convert to any other format you want..i.e. Under/Over,
> Side-by-Side or Anaglyph. There are a number of plugins for Adobe Premier
> to help achieve this.

True.  But, each field has only half the information and resolution (half
the number of scanning lines) of a full frame.  So your results will be of a
much lower quality going this route then going with a dual full frame full
field system.

> I think someone else mentioned that it should also be possible to create
> anaglyph movies directly with the NuView by placing coloured gels on the
> front of the device.

This is a rather inefficient way to do this.  A simple beamsplitter device
(like the NuView, but without the LCDs can be constructed using one front
surface mirror and one dichroic filter.  45 degree dichroics reflect one
color (say, red) and transmit the opposite (cyan).  For display on a
computer monitor this works fine.  For television (NTSC, PAL, SECAM) the
display on the typical receiver degrades the color purity too much so you
will get too much crosstalk in the picture for good 3-D.

> To get back to your particular question, you already have two cameras so
> it should be possible to shoot both streams, load into the PC/Mac and then
> find the matching start frames from each stream. You might have to use
some
> form of clapper board system at the start of each shot, to aid you in
> locating the matching start frames.From this point its simply a case of
> multiplexing both digital streams into one. The plugin
> "CULT EFFECTS Vol 1" by Cycore Computers for Adobe After Effects certainly
> has a filter that will take two streams (left and right) and convert to
> Anaglyph (red/blue or red/green),interlaced (like the NuView) or Stereo
> pair (side-by side). It also lets you dynamically set the convergence.

This is a much better method than extracting streams from already
multiplexed material, as there is no loss.   You have both full fields in
both eye views, and if you want to, you can still multiplex later.  A simple
"finger clapboard" system is to just hold your hand in front of the cameras
and close two fingers at the beginning of each shot.  This is easily edited
out after the two views have been synced in post.  A major advantage of dual
stream acquisition is that once your original camera tapes are in this
format, you can go any direction you want.  You can actually use the same
original content for anaglyph, multiplexed, polarized, prismatic, etc., and
there are no losses other than those you intentionally introduce by the
particular processes.  For example, you can process and view the results as
anaglyph or multiplex, and then if you want to project it at a later time,
you can go back to the original tapes and have a full resolution dual system
with all of the information available to do so without loss.

> I would question your intention of wanting to use Anaglyph. In my
> experience I've never find it to work for video tape.. it just doesn't
> have the bandwidth available to preserve the colour encoding.  Of course
> encoding as MPEG2 and storing on digital medium (DVD/CD) is a different
> story, this defiantly does work satisfactorily.

Correct.  MPEG2 works well with anaglyph as well as any other system where
both fields are used continuously.  However the compression codec causes
problems if you try to compress multiplexed material.

JR



 

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