Mounting and Throw Distances

Most projector use a throw distance of approximately 1.4 to1.5 X the width as measured to the lenses, so for an 8’ wide screen, the lenses need to be 11 to12’ from the screen surface. The exception to this throw distance is the Zenith video projector line that use a throw distance of 1.2 X the width of the screen. This distance can be varied a bit via the height and width controls within the projector, but the idea is to use as much phosphor area of the tubes as possible to avoid premature wear.

The one exception of using too much tube phosphor area is if you buy a projector that has a bit of phosphor wear. If that is the case, the wear area of the phosphor will be a bit less bright than the virgin area. If you project an image onto partial virgin phosphor area, the edge(s) of the image that are into the virgin area will be slightly brighter than the worn area, and an uneven picture will result. The trick to get an acceptable picture from a worn tube is to project the new image within that slight wear area, so that only worn phosphor is used. This may mean shrinking the image down a bit, or moving the projector a bit further back from the recommended throw distance.

Barco throw distance calculator

All CRT projectors may be used in the floor or ceiling mounting mode, front or rear projection. As most projectors have a substantial weight to them, it is obviously important to safely mount the projector to ceiling studs. The other option is to leave the projector on the floor and build it into a custom coffee table or other cabinet. Leave enough room for the projector to get proper ventilation if you are building it into a cabinet.

If a throw distance is not possible due to a room layout, it is possible to bounce the image off an optical grade mirror, thus shortening the distance between the projector and the screen. I have heard of one enterprising individual that mounted a projector behind a couch and then bounced the vertically mounted projector off a mirror located above the couch on top a screen, so that the large projector would not be readily visible.

In general, the projector must also be level with the top or bottom of the screen. If the projector is floor mounted, it must be about level with the bottom of the screen, and if ceiling mounted, the projector must be level with the top of the screen. This can be varied by about a foot or so, but the convergence and geometry alignment allowances within the projector are limited and it is not a good idea to reach the maximum points on a bunch of these settings.

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