[photo-3d] Re: Field sequential movies

[Andrew Woods <A.Woods@xxxxxxxxxxxxxxxxxx>]

A few comments on Elliot's post from two weeks ago...

E R Swanson wrote:
> I'm a film buff with a set of Virtual I/O (I-glasses) and enjoy watching
> 3D movies. The I-glasses aren't perfect, but because there are individual
> monitors in the units, and they retain the image longer than a liquid
> crystal shutter system, there's virtually no image flicker. (The flicker
> caused by the 15 image per second refresh rate in standard field
> sequential systems give me a headache. 

Field-sequential 3D when used with NTSC (60 fields per second) results in
30 fields per second per eye - when view with simple shutter glasses systems,
flicker is visible, but the amount of flicker depends on image and room 
brightness.
When used with PAL (50 fields per second), field-sequential 3D produces
25 fields per second per eye - i.e. slightly more flicker.

> There are higher speed shuttering
> systems for computer applications, but they don't work with the old
> movies.)

The high speed shuttering systems for computer systems that Elliot
mentions are usually just a pair of shutter glasses and an interface
box which drives the glasses in synchronism with the computer's display.
The high refresh rates possible with these systems is due to the improved
technology in the PC these days.  Most new PCs and operating systems allow
the display refresh rate to be set by the user - some up to 180 images per 
second.

Is is possible to view NTSC or PAL without flicker but additional 
devices must be used to modify the video signal (frame double or 
demultiplex).  The cost of such systems is usually beyond the domestic
budget but prices are gradually dropping.  Examples of such systems
are available at: http://info.curtin.edu.au/~iwoodsa/products

Incidentally, as long as the video is field-sequential 3D NTSC or field-
sequential 3D PAL, there is no problem with old 3D movies (or new 3D movies
for that matter).  

Cheers,
Andrew Woods.