How to Set Projector Distancesby Dario Saandvik
When setting up a home theater projector (or even an old film projector), there are a number of factors to consider in determining how far the projector should be from the projection surface. The amount of ambient light in the room plays a big role in how far you can set your projector from the screen. The reflectivity of that surface is also a factor. The size of the picture you want is also something to consider, but it is limited by the light conditions, brightness, projector resolution, and the physical constraints of the theater room. Finally, it is important to consider where you want to sit in the projection room, so that you have a good viewing angle and your head doesn't block the image.
Darken your projection room to match the lighting conditions when you will do most of your viewing. That way you can optimize your setup for best picture quality during the time of day or night that you will use it most.
Arrange your seating so that it faces the screen. Make sure the seats are in roughly the spot where you want to do your viewing.
Mark out a rectangle on the wall with masking tape at the size that you think you want your picture to be. Sit down and see if you can easily see the entire rectangle in your field of vision. If not, you need to either move your seats farther away or make the rectangle smaller. Don't worry about aspect ratios or about the brightness of the projector at this stage of your planning. This is simply to get an idea of what the maximum comfortable image size is for your projection room.
Determine the minimum distance you should sit from the screen based on the resolution of your projector. For a 720p projector, you want to sit about 1.5 times the screen width away so that you don't see the individual pixels, about 1.2 times the screen width for a 1080p projector. Film projectors have an even higher effective resolution, so you could theoretically sit closer without noticing the film grain. Lower resolution projectors might require a smaller screen size.
Place your projector in the back of the room, turn it on, and move it forward until the lighted image fits the area you have marked out. If it isn't bright enough, you'll need to move it closer to the projection surface to concentrate the light. Try watching some content on the projector, to see if you're comfortable with the brightness and your distance from the screen as you've marked it out. If so, then mark that spot as the place to set projector. If not, adjust your masking tape rectangle and try a new configuration.