Posted on August 2, 2011 By Art Feierman
Lens shift is all about a projector’s placement flexibility. Projectors with adjustable lens shift definitely provide more placement options. Since virtually everyone wants their projector setup, up high, rather than just putting it on a table, lens shift is needed to allow you to place a projector on a shelf (in the rear of your room), instead of restricting it to ceiling mounting. This is a huge plus for many owners. First, it puts the projector behind where most people sit (rather than overhead or just in from of the viewer), which helps in making the projector’s fan noise less noticeable. The other advantage for most installations, is that running cabling is usually simpler, and less expensive than ceiling mounting. This is true for several reasons. In most homes, people are likely to have power readily accessible on most walls, on the other hand, most likely people will find that they don’t have a power source in the ceiling. Running power to the ceiling to power the projector tends to be an additional, potentially significant expense. Further, if one has high ceilings getting cabling, as well as power, up there, becomes a lot more complicated than to a back wall.
Another disadvantage of not having adjustable lens shift, is that without it, the projector must be mounted at exactly the right height, instead of over a wide range. As it turns out, those projectors without adjustable lens shift, are designed to be mounted above the screen top. That offset is typically about 18 inches above the top of the screen surface for a 100″ screen, and more or less, depending on the screen size. In more than a few cases, people with normal or low ceiling heights (8 foot or less) find they can’t use a projector with that much offset. For those going with really large screens, say over 120 inch diagonal, you may need a ceiling height of 9 feet, or more. I receive more than a few emails from folks telling me they really had their heart set on this projector or that (without lens shift), but that they couldn’t mount it high enough due to ceiling height.
All projectors with lens shift have vertical lens shift, while not all have horizontal lens shift. Vertical is the important one for most. Horizontal comes into play if you can’t mount the projector with the lens centered relative to the center of the screen horizontally. Thus, horizontal lens shift can be important if there is a reason the projector must be mounted slightly to either side.
Adjustable vertical lens shift means you can mount the projector over a wide range of height relative to the top of the screen. Most typically, a projector with lens shift can be placed anywhere from a couple of feet above the top of the screen, all the way down to below the bottom (talk about flexible). A few projectors have less shift range, although all, to my knowledge, can at least be mounted as high as the top of the screen. I won’t get into horizontal lens shift here (it’s dealt with in the various reviews), but below is a short breakout of all the projectors as to whether they do, or do not have adjustable lens shift.
Most projectors today, except for the more entry level DLP projectors have at least vertical lens shift. All projectors in our mid and top classes have lens shift.
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