I’m thinking of projecting images on a backdrop as part of a tradeshow. How much space between the projector and backdrop do I need to allow? Can I use a mirror (or mirrors) to reduce that distance? How much keystone correction is possible?
Most newer projectors can correct keystone automatically. It won’t work if you’re using a mirror. Also, you’d have to have a pretty large mirror in order for it to have any significant effect in how much room you’ll need. How much space you need will depend on how big you want the image to be. A very rough rule of thumb (read: WAG) would be that you need one and a half feet for every foot of width you’d like to have (this would be about a 60 degree spread).
Also, are you thinking of using plastic slides, or hooking it up to a computer?
I was thinking of hooking it up to a computer. Is automatic keystone correction done by detecting the angle the projector is sitting at?
For the less expensive models, yes. However, when I was fooling around looking at projectors to answer your question, I stumbled across more expensive models that actually “see” the image they project, and use a feedback loop to correct the image.
What kind of resolution are you looking for? Are the images going to have text? How big will said text need to be in order to be legible? Is detail going to be necessary?
As other posters have suggested, a more detailed description of what you’re trying to accomplish might help us provide better advice.
Video projection in a trade show booth is usually less than ideal, for many reasons. It is often difficult to control the ambient light well enough for a good image. With front projection, people in your booth can block the image. Rear projection takes a lot of space outside the booth, requires even better ambient light control, and is technically more complicated.
A large plasma screen could have as much or more impact and would probably be technically simpler to arrange. Is there some reason you’re not considering that?
The technical people at the venue that is hosting the trade show should be able to help you with all of this, and will know companies that can provide the service. Have you spoken to them?
To figure out how much space you need, you need to know the ‘throw distance’ of your projector and how big a picture you are trying to throw. Most projectors have zoom lenses, but will still be somewhat limited in throw.
If the projector has a horizontal flip settnig, you can indeed use a mirror to cut down the projection distance. Most modern projectors do.
For a trade show, I’d be more worried about ambient light. Unless you have a super-bright projector or are going to project into a darkened booth, your picture will be quite washed out. For trade show use, I’d think you’d want at least 3000-3500 lumens for your projector brightness rating.
Most projectors do not correct for keystone automatically. In fact, most people dont like using digital keystone correction because it can distort the picture. Some projectors have a lens that can be shifted a few degrees on each axis to correct for slightly positional problems. If you’re only a foot or two off from the ideal projection location, you can use lens shift to correct the picture without distortion.
Thanks all. I was thinking of using a projector instead of printing a backdrop, I figured that I easily change the picture for different seasons without having to reprint a backdrop. Reading all thr comments here I think that the distance and ambient light will be obstacles to making this look good.