The projector will be, perhaps, your largest single investment in building a backyard theater. The first question is usually, can't I just use the InFocus(TM) from the office? Well, that depends on your office policy. Actually, there are a number of things to consider and below you will find a list of the various options. Since this is going to be a significant portion of your investment, we would encourage you to work with a reputable dealer, we like the ProjectorPeople.
Front or Rear Projection
As the name implies, this depends on where you want to place the projector- in front of or behind the screen. A rear projection machine will flip the image so that the audience will see the picture in the correct orientation. The advantage of rear projection is that it allows you to maximize the seating area in front of the screen. The disadvantage of a rear projection machine is that, depending on your screen, you may lose some intensity of the picture which will delay the starting of your movies until the sun has set a little more. Our experience is that the extra setting area far exceeds the extra wait to start the movie, and actually, we start the movies at about the same time either way.
This cool feature is relatively new. What it allows you to do is off-center the projector from the screen. This allows you to reclaim seating space in front of the screen and to safely position your equipment on the side.
This is the measure of the intensity of the light from the projector. For outdoor applications, you will want to look for something between 2500-3000 lumens. The higher the lumen rating the earlier you can start the movie... that, at least, is the theory.
The Keystone control is the projectors ability to compensate for the tilt of the unit. The keystone adjustment (automatic or manual) will place the image on the screen back into the correct position so images do not appear elongated.
All projectors will list a resolution, for example, 848x480 pixels. You will want to match the resolution of your projector to the types of movies you're most likely to be playing; typically 1280x720
If you are hoping to create a Blu-ray type experience outdoors, the reality is that it's probably not going to happen. While today's projectors are very good, you're likely going to lose some picture quality by the time it hits the screen. The good news is, don't worry, a good picture quality with good sound and the awesomeness of being out under the stars makes up for any loss in picture quality.