Lens Throw and Lens Shift
Some projectors have a lot of placement range, while others are severely limited. With few exceptions, 3LCD projectors and LCoS projectors are extremely flexible, with zoom lenses with plenty of zoom, and all of these two groups of projectors have lens shift. By comparison, the DLP projectors consistently have very little zoom range. Some of the DLP projectors have lens shift others do not. Even when they do have lens shift, they don't have as much as the other types.
Let's discuss the issues, then get into the individual projector's abilities.
Lens shift is a requirement if you want to shelf mount a projector in the rear of your room. It allows the projector to maintain a proper, rectangular image on the screen from different heights, and for a projector placed higher than the mid-point on the screen, without lens shift, the projector must be inverted, so, essentially, ceiling mounted.
The other thing you need to shelf mount, is a projector that can be placed far enough back to sit on a rear shelf. Of course your room length and screen size come into play. Let's say that those projectors without lens shift normally also have lenses with very little zoom range, so their throw distance range is normally kept fairly short, figuring that ceiling mounting is easier, closer to the screen.
Here's a chart organized by our three Classes. For each projector, it provides placement information in terms of distance and height, for a 100 inch 16:9 screen. Using these numbers, you can determine the ranges for any sized screen just with a simple calculation.
All of these projectors can be ceiling mounted. All of the projectors with lens shift are capable of rear shelf mounting.
Note: All numbers above are approximate. Throw distances should be accurate within about one inch. In terms of Maximum shift, and especially the amount of shift (offset) on projectors without adjustable lens shift, we have found that manufacturers often make errors!
We recommend you double check the numbers with the manufacturer's tech support, for accurate lens shift numbers. If you are using an installing dealer, they should be on top of the situation. (At least two of these manufacturers show conflicting information in their brochures, compared to their manuals, on at least one model.
For your convenience, below, the home theater projectors are organized first by price class, then by amount of placement flexibility. The four categories are:
Greatest Placement Flexibility (excellent zoom range, lens shift)
Good Placement Flexibility (moderately good zoom range, lens shift)
Fair Placement Flexibility (typically limited zoom range, lens shift, there are exceptions)
Poor Placement Flexibility (limited zoom range, no lens shift)
None of the projectors listed as Poor can be shelf mounted. Those rated Fair can be shelf mounted, but have very limited range and may not work out in most rooms.
Keep in mind that if you plan to ceiling mount, there isn't that much difference between the four groups, unless ceiling height is an issue, in which case Poor Placement Flexibility projectors may still be a problem as they lack any lens shift.
The key benefit of ceiling mounting is that you can place the projector closer to the screen which often means a brighter image.
Key benefits of shelf mounting include usually easier to get power to the projector (installation time and cost), less audible noise, easier access, generally simpler to install and align.
Mid-Priced 1080p Projectors - $2000 - $3500
Greatest Placement Flexibility: Epson Home Cinema 5010, Epson Pro Cinema 6010, Panasonic PT-AE7000, JVC DLA-RS45
Good Placement Flexibility: BenQ W6000, LG CF181D, Mitsubishi HC7800D, Sony VPL-HW30ES, Vivitek H5080.
For the second year running, this year, every projector in this mid-priced class offers lens shift! All of them have at least a 1.5:1 zoom ratio as well. In other words every projector we reviewed in this price range had at least good placement flexibility. The most signficant difference between "Greatest" and "Good" placement flexibility is that most of the "good" ones may not work rear shelf mounted, if your room is moderately deep, or your screen relatively small for the room size. those with 2:1 zooms normally can be shelf mounted in all but very unusual (read very deep) rooms, even these "greatest" projectors won't be rear shelf mountable (with a 100" diagonal screen) in rooms deeper than about 22 feet.
Premium Priced 1080p Projectors - $3500 - $10,000
Greatest Placement Flexibility: JVC DLA-X70R, Runco LS5 and LS10d (interchangeable lenses), SIM2 Nero 3D-2 (interchangeable lenses)
Good Placement Flexibility: Mitsubishi HC9000D, Optoma HD8300, Sony VPL-VW95ES
All projectors in this class have lens shift as well! This year every projector without lens shift, sells for under $2000. Last year, we had some projectors without lens shift, in all three price classes. What has changed? Primarily the DLP projector manufacturers have been getting tired of losing sales to the LCD camp, because of placement flexibility.
Ceiling Height Issues: These projectors are less likely to work in your home theater if your ceiling height is low, or if ceiling height is average, but screen size is rather large. This is due to a lack of lens shift, combined with a signficant amount of fixed lens offset, that requires them to be mounted well above the top of your screen. All of these must be mounted at least 7.5 inches (measured from the center of the lens) and up to 16.5 inches above the top of the screen.
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 distance between ceiling and center of the lens:
| 7 feet
| 8 feet
| 9 feet
| 10 feet
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, take for example, a projector like the Mitsubishi HC4000 (has 16.5 inches offset). 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.
Projectors with lens shift:
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.