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Key features

Throw distance

Just like your digital camera, a projector also comes with an attached optical lens for focusing and zooming. Putting aside the nitty-gritty such as lens aperture, you'll have to consider two major parameters to determine a beamer's throw capability: Throw ratio and zoom factor. A short throw model, for example, will require less projector-to-screen spacing to produce a sizeable image.

To factor for both standard and wide aspect beamers, the throw ratio is calculated by dividing lens-to-screen distance with the length of the projected image. This works out to a large projection in a shallower space given a low value, and vice versa. A zoom-capable lens will have a similar effect, except that this is a case of the higher, the better; while you tend to lose some screen luminance, the more powerful it gets.

Lens shift/Digital keystone

These affect ease of installation by manipulating the alignment of the projection. With lens shift, you don't have to line up the beamer perfectly with the screen. Best of all, this has minimal picture quality penalty since it physically repositions the lens within a range. Vertical and horizontal lens shift are almost standard in LCD/LCoS home theater projectors and considered a luxury for others.

Digital keystone adjustment is used to correct geometry distortions such as a skewed trapezoidal image due to a hasty setup, uneven support, etc. Unlike lens shift, vertical keystone is a given in most current offerings and have been further automated in some cases. The only caveat is a detrimental impact on the visuals in sharpness. Horizontal keystone is also available, but hardly mainstream.

Video processor

This is another norm to cover common video post-processing, such as scaling an incoming feed to match the projector's native resolution or applying noise reduction. Going one step further, home theater beamers have dedicated engines that perform other nifty stuff. These include interlace-to-progressive scan, video-to-film frame-rate conversion, advanced edge enhancement, and more.

Among the popular chips are the PixelWorks DNX, Faroudja DCDi Edge and an improved DCDi Cinema, followed by the enthusiast-grade HQV Reon-VX and flagship HQV Realta exclusive for premium models renowned for their jaggie-free HD upscaling performance. While most chips are integrated right into the projectors, the Optoma HD81-LV's version is installed in an external box.

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