Richard D. Clark wrote:
>
> Hi, folks!
>
> I'd like to discuss, with someone who's worked on a permanent (or
> long-term) exhibit that incorporates chroma-key ("blue-screening" or
> "green-screening") video technology, the technical issues involved.
>
> I'm particularly interested in solutions to the problem of lighting
> the "stage" area evenly without the subject casting shadows on the
> backdrop, but without using expensive, hot, dangerous theatrical
> lighting instruments.
>
> I'm also looking for a technology that allows superimposing the
> subject onto just a portion of the frame.  Normally the blue backdrop
> must correspond to the NTSC video frame on a 1-to-1 basis (so to
> superimpose a tiny person you need a huge backdrop).  What I need is a
> way to have a person standing in front of, say, an 8-foot tall blue
> screen, be superimposed onto just a corner of the video frame.
>
> Responses either via e-mail or to this list will be read and
> appreciated.  Thanks!
>
> _______________________________________________________
> [log in to unmask]            Interfacing is Easy
> [log in to unmask]                                    ....
> [log in to unmask]        Compatibility Takes a Lifetime


I just finished a chromakey exhibit for the Columbia Gorge Discovery
Center where we key a person on a surfboard in the museum with a video
videodisc background of big waves on the river. I can assure you it is
fraught with sticky issues.  You're absolutely right about the shadow
problem.  The key is even lighting of the BG with a high key light for
the subject, subject placed far enough from the bluescreen to avoid
shadows. Keeping the camera height down to eyelevel also helps. Careful
setup of the camera is important, and avoid anythig that autofocuses.

This museum had an extremely limited budget so we went fairly cheap:  A
Videonics MX-1 digital mixer, Elmo CCD camera with S-video out, and
Pioneer Laserdisc for background footage. One problem is that the MX-1
will not remember any settings when power is removed.  We've suggested
they just leave it on all the time, but it does get shut off.  Then a
staff person needs to not only put it back in chromakey mode, but also
has to go through the background color calibration process.  Only takes
a minte, but it's still a pain.

Still it's a hit.


Contact me directly my email to discuss some of the more specific
issues.

Jim Swenson
New Media Magic
Interactive Exhibits