Posted on March 14, 2008 By Art Feierman
One dramatic improvement (I think so, at least) is that this year, most of the projectors lacking adjustable lens shift, have been redesigned compared to previous models, so that they have less fixed lens offset. Last year we had 5 projector with at least 15 inches of fixed offset. This year, that number has dropped to just one, (the Mitsubishi HC3800 at 16.5 inches offest) and only one other with at least 10 inches (that would be 12 inches for the Samsung SP-A600. The rest of the fixed lens offset projectors all have about 8 inches of offset, which is just about half of what most of last year’s units offered!
The same chart we used above for throw distances has almost all the info you need for vertical positioning. It tells you if the projector has adjustable lens shift, and where the projector can be mounted, relative to screen height. Below is a list of projectors that do not have lens shift, and do have a lot of lens offset requiring them (if ceiling mounted) to be mounted higher than the top of the screen, by enough that they may not work in your room, if you don’t have higher than average ceilings.
All of these units must be mounted approximately 17 inches above the top of your screen’s surface. That 17 inches is the difference between the top of the screen’s surface, and the center of the lens. Remember, that even mounting as close as flush to the ceiling as possible, the center of the lens is likely going to be at least 7 inches below the ceiling (and that’s tight).
Below is a chart which gives several examples. It tells you how far off the floor the bottom of the screen surface (not the frame) would have to be, for four common screen sizes, and four different ceiling heights. Obviously, you can’t have your screen starting just a few inches off the floor, especially if some folks sit behind others. To come up with these numbers we assume a projector without adjustable lens shift, fixed lens offset of 15 inches, and the center of the lens. We assume you can’t mount the projector any higher than where the center of the lens would still be 7 inches below the ceiling (about as high as you can mount it, with a typical ceiling mount). Many mounts may require an even larger.
Screen size (above) is diagonal screen size, measured in inches.
Measurements (inches) provided are distance from floor to bottom of screen surface (not screen frame).
As you can see from the chart above, if you have a projector like the Mitsubishi HC3800 (has 16.5 inches offset, the most of these projectors. For it, an 8 foot ceiling, and a 110 inch diagonal screen, the bottom of your screen surface is about 20 inches from the floor. That’s certainly about as low as anyone would want. With the same 8 foot ceiling, and a 128″ screen (like mine), you’d have to dig a hole, as the bottom of the screen would be below the floor level!
If your setup is going to be tight, you may want to start by figuring out how close to the ceiling, you can mount the projector. Then add the distance to the center of the lens which will vary depending on how far (vertically) from the top of the projector to the center of the lens.
Distance from ceiling to top (inverted) of the projector + Distance from top of projector to center of lens = Total distance from ceiling to lens center.
Bottom line: This year’s projectors, as a group, are far better than last year’s when it comes to vertical placement flexibility. For openers, not one over $2000 projector in our report lacks adjustable lens shift. Last year we had 3 higher priced projectors without lens shift. In fact, despite the addition of three new entry level $999 projectors without lens shift, this year’s crop of projectors finds that lens shift is finding its way on to more and more DLP projectors (it’s already standard on all LCD and LCoS projectors we reviewed.
Since all the other projectors have adjustable lens shift, your only restriction to screen size is if it fits on your wall, with the minimum height off the floor that you find acceptable (without the top of the projector hitting the ceiling).
For example, with that 128 inch screen and a projector with lens shift, the screen height (excluding frame), is about 63 inches. Thus, even with an 8 foot ceiling height, you could have the screen surface bottom as high up as 33 inches (96 inch room height – 63 inches of screen height = 33 inches). Now that would have the top of the screen flush with the ceiling, and doesn’t allow for the screen’s frame, so if you have a four inch frame at top and bottom, the 33 inches becomes 29 inches.
Please remember, we calculate the lower number from the bottom of the screen surface, not from its frame, so the bottom of the frame would be at 25 inches (29 – 4) with a four inch wide frame.
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