km@mathcs.emory.edu (Ken Mandelberg) (02/21/89)
We are looking for an overhead projector to use with
an LCD display. The few spec sheets I've seen are all
for 3M models that seem very similar, yet I would think
that there should be:
* some variation in optics. Are there models that could be
positioned closer to the screen?
* some variation in brightness. Are there projector/screen
combinations that perform better where brightness is
critical?
* some variation in light path. Are there models that would
work with a permanent wall or ceiling mount? When used with
an LCD the display surface does not have to be accessible
to the speaker.
Any A/V experts out there?
--
Ken Mandelberg | km@mathcs.emory.edu PREFERRED
Emory University | {decvax,gatech}!emory!km UUCP
Dept of Math and CS | km@emory.bitnet NON-DOMAIN BITNET
Atlanta, GA 30322 | Phone: (404) 727-7963soley@ontenv.UUCP (Norman S. Soley) (02/22/89)
In article <3733@emory.mathcs.emory.edu>, km@mathcs.emory.edu (Ken Mandelberg) writes: > We are looking for an overhead projector to use with > an LCD display. The few spec sheets I've seen are all > for 3M models that seem very similar, yet I would think > that there should be: > > * some variation in brightness. Are there projector/screen > combinations that perform better where brightness is > critical? I've used one of these units and experience shows it's best to avoid reflective screens for this application, a "dull" white screen is best, I use a big piece of foamcore or just white paper "tablecloths" > * some variation in light path. Are there models that would > work with a permanent wall or ceiling mount? When used with > an LCD the display surface does not have to be accessible > to the speaker. No but in some of the units there's a fairly small spot that has to be hit with the remote control unit (not just for special effects but also for adjusting focus and contrast), be careful to keep that spot within "shooting distance" of the speaker. -- Norman Soley - Data Communications Analyst - Ontario Ministry of the Environment UUCP: uunet!mnetor!ontmoh!ontenv!soley | Contents of this message are OR: soley@ontenv.UUCP | my ideas, not the Ministry's "Stay smart, go cool, be happy, it's the only way to get what you want"
jhenry@randvax.UUCP (Jim Henry) (03/04/89)
Overhead projectors do come with different focal length lenses which affects how big the image is at a given distance from the screen. If you know how far the projector will be from the screen and how big the screen will be then you can figure what focal length lens you need. You'll probably have to do some compromising here, there are limited choices of lenses and overhead projectors usually find themselves in varying projection setups. Brightness is affected by the lamp wattage, lamp type, and projector optics among other things. Usually quartz lamps are the brightest. More watts for the same kind of bulb will be brighter. Reflective optics (lamp above the transparency in the projection head) gives a compact projector but I've never been impressed with their brightness; also I understand that these don't work well with LCD displays. I used to use a projector that used a mirror rather than the more common fresnel lens for a condensor; it had outstanding brightness. You really need to try the projector, preferably side by side, to evaluate brightness. The most important factor with LCD displays is heat. As the display gets hot its contrast falls off. The worst problem is if the light intensity and heating are not uniform across the display. You'll wind up not being able to get all of the display to project at the same time. Again, you really need to try the projector and for an extended period of time. Having used an LCD display for a presentation, I would be seriously tempted to use conventional transparencies of screen shots if at all feasible, particularly if I had to present to a lot of people. If I really did need the "live" demo I'd also seriously consider having an assistant to run the computer while I did the presentation. It is pretty hard to do a good presentation and work a computer at the same time. On the other hand, LCD displays are great if you want to do a demo for more people than you can crowd around your computer but you aren't doing some big formal presentation.