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Re: projectors



At 09:50 AM 4/18/01 -0600, Larry Smith wrote:

aside
from the cost, there is another reason I think overhead projectors won't be
replaced by TV cameras or document cameras: the overhead projectors have a
much greater resolution. I love my document camera (Elmo) for many things
and use it often. It has some flexibility overhead projectors don't (for
example I teach HP calculators by putting the calculator on the Elmo), but
for fine detail diagrams I've yet to find anything as good, cheap, and
convenient as the overhead transparencies.

Projection technology is changing. A few years ago, a VGA projector was
$20,000, big, noisy, not very bright, and not very sharp in
resolution. Now for $3,000 you can get something that is small, quiet,
bright enough for a 1000-seat auditorium, and sharp as a tack. (The
difference is that they have started using micro-mechanical mirror
arrays. Neat physics.)

Here's an overview:
a) 99% of the time when I'm giving a talk I project it straight out of
my laptop, using a digital projector.
b) 0.9% of the time I need to improvise something, so I use an overhead
projector, and use pens to write on blank foils. So we will keep the
projectors around.
c) The remaining 0.1% of the time, my talk is being telecast to some
other location *and* I have non-electronic documents to show, so I use the
document camera. But we are getting pretty low on the food-chain here.
d) The digital projector will also accept composite video (or, better,
separated video). That means you can point a camera at a lab demonstration
(meters and all) when desired. This does not generalize to fine documents
because of the limited resolution of the camera.


BTW --- Given the geometry of an ordinary room, people in the back aren't
going to be able to see fine details no matter what technology you use,
because the screen subtends a too-small part of their field of
view. Therefore: use large fonts and large scale-factors in all your
materials.

You can alleviate this to some extent by having multiple screens. You feed
N projectors from the same signal. If this is set up properly it works
quite nicely.