Ceiling-mounting your LCD projector? Read this first

Most projector ceiling mounts offer a simple and stylish solution that attaches to the underside of the projector and then to the ceiling, effectively hanging the projector upside down. This, however, isn't always the best solution.

The diagrams below show how the lens-shift function works in three different tri-LCD projectors.


The projector is located where the dotted horizontal and vertical lines cross each other. The coloured zones represent the maximum shift of the projected image in all four directions. The purple rectangle is cut off as it overshoots the limits of our physical frame. In other words, the lens-shift is greatest in this direction.

The diagrams show that all three projectors are clearly better at lowering the projection zone rather than raising it i.e. they're better at moving the purple block down than moving the green block up. So what happens when you turn this type of projector upside down? Logically, it becomes better at moving the projected image upwards, i.e. onto the ceiling. Practical ... for giraffes.

The right way up?

Ceiling-mounting a tri-LCD projector can cause problems if you have a high ceiling but need a low projection zone. As the projector will be mounted upside down, the picture will be projected too high and it'll be impossible to move it down low enough. You'll be straining your neck trying to watch anything. If this happens, the worst thing you can do is try tilting the projector and using the trapezium correction function (if available). It won't help that much and it'll affect video quality. The best thing to do is turn the projector back the right way up, and simply stand it on a high shelf, for example. That means you'll be able shift the image down into your desired viewing zone and you won't have to crane your neck to watch a film!

What about DLP projectors?

DLP projectors pose a different problem entirely. Given that they don't normally have a lens-shift function, the image is projected at a fixed angle (see picture, right). The wider the angle, the more likely it is you'll need to ceiling-mount the projector upside down. However, as the angle can't be adjusted, finding the best position is basically just a question of trial and error.

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