In "How To Buy A Home Theater Projector, Part 1: Behind the Lens," we covered front projection fundamentals: the key parts of every projector, differences among light sources and imaging technologies, and projection screen basics. Here in Part 2, we'll discuss projector installation, how to determine projector throw distance and brightness requirements, what features you should look for in a home theater projector, and how to use ProjectorCentral's powerful projector database to zero in on models that suit your specific needs and budget.


Projector Installation

Before you can select a home theater projector there are some practical matters to think about including placement of your projector and screen, the screen size and material, and the mechanical installation.

The simplest installation is one in which you pull a projector out from the storage closet each time you want to use it, set it up on a coffee table, and project onto either a wall (poor choice) or a portable or retractable screen (better). Most permanent installations, however, end up with the projector mounted upside down from the ceiling or placed on a tall shelf or in a cubby at the back of the room. These installations may require not just physical mounting of the projector, but possibly the wiring of a power outlet near the projector (typically done by a licensed electrician), and the running of signal cables inside the ceiling and walls to reach from the source components to the projector location. It's skilled work that a DIYer may or may not feel confident about.

Ceiling mounted projector3
Cubby mounted projector 800
Most permanent installations utilize a ceiling mount with the projector inverted; a setting inside the projector flips the image appropriately. Below: A rear-wall shelf or cubby mount may be less obtrusive, but be sure to account for proper ventilation.

You can, of course, hire a custom electronics integrator/installer to do the work and help you select your projector and screen. That's a highly recommended path that takes all the complexity out of the process and insures a good result. The website of the Custom Electronic Design and Installation Association has a locator to find reputable member companies in your area.

Another option is to consider one of the new 4K UST TV projectors mentioned in Part 1 of this article. These projectors are designed for tabletop placement on an A/V cabinet or credenza situated just a few inches below the 100- or 120-inch screen. Since your TV set-top box and other source components reside in the cabinet, there are no wires to run through walls or ceilings. You can learn more about this category and the available projector and screen products in our Ultimate Guide to 4K Ultra-Short-Throw TV Projectors.

LG HU85LA Lifestyle1
Today's ultra-short-throw laser projectors produce bright images in ambient light when mated with an appropriate screen while avoiding the need for in-wall or in-ceiling cable runs.

Buying a Projector Step 1: Projector & Screen Placement

If you've been thinking about an installation you probably already know where you want to put the projector and screen. The likelihood is that architecture or pre-existing seating in your room will restrict the screen placement to one particular wall, and it's just a question of where to put the projector. If you end up with a ceiling mount, you'll ideally want the projector somewhat behind the viewers or closer to the front of the room rather than directly above the primary seating, which will minimize the audibility of fan noise that every projector emanates—some more than others. Whether you ceiling- or shelf-mount your projector, you'll want to keep it aligned with an imaginary vertical line drawn down the center of the screen, rather than off-center to the left or right. This will avoid the need for horizontal lens shift and reduce the likelihood of issues with keystone distortion that disrupts the rectangular geometry of the image.

PC Calculator throw distance 1a
PC Calculator throw distance 2a
Throw distance is the distance between the projector's expected lens location and the screen. ProjectorCentral's Throw Distance Calculator can show you the throw distance for a given screen size with any projector in our database. These illustrations show the shortest (11 ft, 9 in) and longest (24 ft, 9 in) possible distance with a 120-inch diagonal 16:9 screen screen for a projector with a long 2.1x zoom lens.

Once you know the expected location of the projector and screen, you can measure the approximate "throw distance" between the projector lens and the screen surface. This is a critical piece of information you'll need to choose a projector. Later on, you can use ProjectorCentral's Throw Calculator, or one provided online by the projector manufacturer, to determine if a projector's lens will accommodate your space requirements.

Buying a Projector Step 2: Determine Screen Size

Along with your projector and screen locations, your primary seating distance will likely be self-evident. There are industry recommendations for how large a commercial theater screen should be for a given seating distance, with the idea of optimizing the viewing angle for the patrons' peripheral vision. SMPTE, the Society of Motion Picture & Television Engineers, suggests a 30-degree viewing angle from the center sweet spot to the far left and right edges of the screen. THX recommends a 36-degree angle, which would make the picture a bit more immersive. You can visit this online screen distance calculator to see the screen size for each of these with your given seating distance. To give you some idea, if you had a 15-foot viewing distance, the SMPTE recommendation would result in a 110-inch diagonal 16:9 screen, while the THX recommendation would result in a 134-inch diagonal screen.

The reality, however, is that these are only recommendations, and your decision will ultimately be based on your personal taste and your available space, as well as your desire to stay within the most cost-effective, industry-standard screen sizes. Do you like to sit further back in the movie theater, very close-up, or somewhere in the middle? And how large a screen can you physically fit on your wall?

Viewing angle vs distance2
As the distance from the viewer to the screen shortens, or as the screen gets larger for a fixed distance, the viewing angle widens. This results in more engagement of peripheral vision. Most experts agree that a 30 to 40 degree viewing angle is ideal for home theater, but what's right for you is a matter of personal taste.

Screens come in standard sizes, give or take a few inches each way. For the average home theater, you'll likely be looking at options in the 92- to 150-inch diagonal range for a 16:9 aspect ratio screen, with 100-, 110-, and 120-inch being among the most effective and popular. A great way to zero in on the right size for your room is to tape out a box on your wall with removable painter's tape using the width and height dimensions of your proposed screen. Then sit back in your viewing chair and see how it feels. You'll know instantly if you need to go up or down a size.

Buying a Projector Step 3: Determine Projector Brightness

This is the last step before you can go scouting for projectors, and it's an important one. Let's start with some basic definitions and concepts. Projector brightness is specified in units of "lumens." The major projector brands cite "ANSI lumens" or the nearly equivalent "ISO 21118 lumens," which refer to a pair of industry-standard measurement techniques and allow the brightness of projectors to be directly compared (more or less).

While a projector's maximum lumen output is fixed by design, the amount of brightness it delivers to your screen for reflection back to you will vary based on screen size and other criteria discussed below. This realized brightness is typically measured in "foot-Lamberts," abbreviated ft-L. Ft-L is not a projector specification, but rather a measure of performance you could determine for yourself with a light meter.

BenQ ProjectorBrightnessComparison2
While a projector's maximum lumen output is fixed by its engineering, the amount of brightness realized at the screen is affected by the image size and ambient lighting. In this simulation (courtesy of BenQ), the projector on the left would require a higher lumen output to achieve the same image brightness because of sunlight from the windows.

Note that brighter is not necessarily better with home theater projectors. Too much brightness in a dark theater can actually lead to viewer fatigue, and the brighter you go the harder it is to maintain lower black level and superior contrast. This is why many premium projectors regarded as having the best contrast and deepest blacks come in with ratings of less than 2,000 ANSI lumens, though projectors intended for bright-room viewing may go to 3,500 lumens or more.

There are some established targets developed for movie theaters to describe how many ft-L you might want coming off the screen in a dark room. SMPTE suggests 16 to 22 ft-L for a dark theater, but many home theater viewers prefer somewhat brighter images. These days, especially if you plan to watch a lot of High Dynamic Range (HDR) content from a 4K home theater projector (more on that below), it's safe to target up to 25 to 30 ft-L as a minimum, though you'll need less for regular Standard Dynamic Range (SDR) programs.

As mentioned, the amount of ft-L that arrives at your screen for reflection back to the viewers depends on two other key factors besides the projector's lumen spec. First is the image size. The larger the image, the greater its area, and the more lumens are required from your projector to achieve a given brightness across the entire screen.

The other critical factor is the amount of ambient light interfering with the projector's output. If you plan to watch in a bright family room, you might want as much as 50 ft-L or more at the screen so it'll punch nicely through the room light—though use of an ALR screen can reduce that need somewhat by improving contrast and keeping the darker areas of images from looking washed out.

One more factor that needs to be accounted for is the screen gain. A screen with gain higher than 1.0 will take the light delivered to the projector and throw it back brighter, resulting in more ft-L presented to a viewer sitting at center screen. Similarly, a lower-gain below 1.0, as is sometimes found with ALR screens, will reduce the ft-L at the center seat. You can calculate the effect of screen gain on lumens just by multiplying: a 1.3 gain screen, for example, will deliver 1.3x the incoming brightness from the projector back to the viewer, or about 30% more brightness. We covered the subject of screen gain in Part 1 of this article, and you can also read more in our Tech Talk article "What is Screen Gain."

Another ProjectorCentral Tech Talk article, "A Simple Guide to Calculating Lumens," goes into detail on all this and also provides an easy formula to calculate how many ft-L you'll get from a projector's given lumen count for different screen sizes:

lumens = ft-L X screen area in square feet / screen gain

Though the formula is simple, calculating the screen area from the screen width and height can be cumbersome, so our article provides a handy table with the screen area of popular diagonal screen sizes in the 16:9 aspect ratio.

When you start shopping, you'll find that traditional home theater projectors range from about 1,500 to perhaps 3,500 ANSI lumens maximum brightness. However, you won't be seeing all of that on the screen, because the projector's brightest preset viewing mode often displays visibly tinted color you won't want to use for watching movies or TV. In fact, it's best to assume that the projector's most color-accurate modes will deliver about half to two-thirds, give or take a bit, of the projector's full brightness spec.

ProjectorCentral's product reviews usually list the results of our measured lumens test for each of the projector's color modes to help you judge. But in the absence of confirmed measurements from a trusted source, you can always guesstimate. As an example, if you use the formula and do the math, a 1,200 lumen projector with a 100-inch diagonal, 1.0-gain, 16:9 screen will deliver about 40 ft-L coming off the screen in a dark room. Cut that in half to account for selection of a less-bright, more color-accurate picture mode, and you're left with about 20 ft-L. So, you might consider 1,200 lumens about the very bare minimum for dark-room theater on a 100-inch screen. If you raise your threshold to 1,500-1,800 lumens, you'll have some room to run things a little brighter in the dark or turn on some degree of ambient light. At a 150-inch diagonal screen size, you'll need about 2,600 lumens instead of 1,200 lumens for similar 20 ft-L brightness.

Sony VPL-VW295ES
4K Home Theater Projector
Sony VPL-VW295ES
4K Home Theater Projector

Note that you'll find more home theater projectors today spec'd at 2,500 lumens and higher than ever before. Projector manufacturers have acknowledged that more people are using projectors as TV replacements for binge watching and sports, and have adjusted their designs to ratchet up the brightness to account for some degree of ambient light. With some exceptions, you'll usually find that the extra brightness above 2,500 or so lumens comes at the expense of slightly less accurate color and a sacrifice in contrast performance compared with a given brand's similar dark-room projectors, but these projectors still provide an essentially accurate and highly satisfying image.

Buying a Projector Step 4: Find Your Projector

At this point, you should know your screen size and your throw distance, have at least a notion of the expected screen gain, and have been able to calculate about how many lumens you need for your situation. Congratulations—it's time to actually start culling through projector specs, features, and product reviews to find just the right model.

Fortunately, we've got you covered in a big way. ProjectorCentral's greatest claim to fame is our unique projector database that lists more than 11,000 current and past projectors, representing a virtual history of the category for the more than two decades of our existence. Our Find a Projector feature, available from the homepage, lets you search by a wide range of criteria, including Type/Application (i.e., Home Theater), Brightness (lumens), Resolution, Price, and others. Each projector found in your search has its own information page that includes key specs as well as links for downloading the spec sheet and user manual, and a link to our proprietary Projector Throw Calculator so you can assess whether the zoom lens will accommodate your throw distance. If we've reviewed that projector or awarded it in any way, you'll find links to those articles as well. Finally, for most models that are available online, you'll usually see a current price link that will take you to one or more authorized projector resellers you can consider purchasing from.

PC Find a ProjectorSearchEngine
ProjectorCentral's unique Find a Projector search engine has thousands of projectors in its database that can be filtered by a wide range of technologies and features.

Another great resource to consult are our Top Ten Home Theater Projectors lists provided for different price brackets. Though these rankings are not curated editorial recommendations, the lists are generated by constantly monitoring web traffic to our Find a Projector database, the price-quote engine connected with our affiliated projector resellers, our Projector Throw Calculator, and our editorial product coverage and reviews to gauge which projectors are generating the most buzz and sales activity.

Projector Specs & Features

What should you be looking for in the way of specs, features, and performance? We've got a basic list below, but be aware that aside from overall brightness, the specs don't really tell you much. Projectors with very similar specs on paper often perform very differently. That's why it's so important to seek out and read expert and user reviews before making a purchase.

Brightness. Like the horsepower spec on an automobile or motorcycle, a projector's brightness spec tells you what kind of muscle it's got. We've discussed brightness above, but know that a projector from a reputable manufacturer will usually be marked in ANSI lumens or ISO21118 lumens. The exception is that LED projectors will sometimes be specified as having "LED lumens" as an ANSI equivalent. In this case, the manufacturer is saying that the perceived brightness is equal to what you'd get when measuring the ANSI lumens of a lamp-based projector, even though an actual ANSI measurement of the LED projector results in a lower number. You can read more about LED lumens in our article, "Are LED Lumens a Real Thing?."

Otherwise, if a projector's brightness specification is not clearly labeled ANSI or ISO lumens, you cannot properly judge its brightness against other projectors and the product or manufacturer should be viewed as suspect. Keep in mind, too, that even if a product comes from a reputable brand and is marked as having ANSI lumens, that maximum brightness still might not be achieved at the projector's brightest settings. We always conduct a standard 9-point ANSI measurement as described here on every projector we test, and they don't always meet spec—although they're usually within or close to the 10% ANSI tolerance.

ANSI lumens measuring points
Measuring ANSI lumens involves taking measurements at each of the nine points indicated by the large black dots shown here.

Contrast Ratio. A home theater projector's contrast ratio is an important performance criterion, defined as the difference between the darkest black and brightest highlight the projector can reproduce. Contrast is what gives images dimensionality, makes black look black on darker scenes instead of a washed-out-gray, and makes shadow details and gradations more visible in darker areas of the picture. Unfortunately, the contrast ratio specifications provided by manufacturers are misleading and meaningless for comparing projectors of different brands. Unlike with brightness, there is no universally accepted standard or technique for reporting contrast ratio, and the competitive marketing among brands has devolved into a ridiculous apples-to-oranges numbers game. These specs are only useful for understanding which projectors in a single manufacturer's current line-up are the highest performing. You'll have to read reviews to confirm a projector's real contrast performance.

Nonetheless, good contrast ratio and deeper blacks is one of the most visible attributes of better projectors, and often the most important reason to step up and pay more for one. There are two key engineering decisions that affect a projector's contrast. First is the native black level of the imaging devices themselves. If the imagers can only make light gray instead of something closer to black, overall dark scenes will have a washed-out haze over the image that's clearly visible when viewing in a dark environment. Deep native blacks, on the other hand, allow the projector to reveal fine gradations of light in dark areas and provide added dimensional realism and punch to every scene.

Beyond the native contrast of the imagers, projectors will usually have some kind of mechanism—either a dynamic iris or dynamic contrast signal processing—to adjust the brightness on darker material and make the blacks appear deeper and richer. In the absence of deep native blacks there's only so much these tricks can do, but even the best projectors usually benefit from them. Better dark-room home theater projectors will have a dynamic iris; it's a feature to keep on the lookout for.

Panasonic Dynamic Iris
A dynamic iris can take different forms, but usually involves flaps that partially block the beam coming off the light source to improve contrast on dark content. (Photo: Panasonic)

All of that said, while contrast performance is always important and particularly so for dark-room home theater, ambient light is the enemy of contrast and even small amounts of it will usually make it impossible to see fine differences in black level and contrast among projectors. If you plan to do most of your viewing with the lights on, it may not make sense to pay more for a projector with better contrast when all other things are equal.

Resolution. Ultra HD/4K resolution of 3840x2160 pixels is now the norm for new flatpanel TVs, but the projection world has been slower to adopt 4K and still brings out many new 1080p (1920x1080) projectors each year. You can get a very good 1080p home theater projector for about $500 today and a quite excellent one for $750-$1,000. It's a great and cost-effective entry path into truly bigscreen home theater.

That said, if you can spend closer to $1,500-$2,000 on your projector alone, which puts you in a sweet spot among budget UHD models, there are a number of benefits to stepping up. First, the additional detail provided by the extra pixels on the screen—approximately 8.3 million in a full UHD projector vs approximately 2.1 million for 1080p—are much more valuable and visible on a 100-inch or bigger projection screen than they are on a 65-inch flatpanel TV being viewed from 10 feet away. More critically, a UHD projector opens up the world of 4K content from streaming services and ideally UHD Blu-ray discs, which offer more than just extra sharpness. Better UHD projectors will also do a great job with content mastered for High Dynamic Range (HDR), which can demonstrably boost the brightness of highlights and further improve contrast. And they may offer the wide color gamut used to master UHD content as described below. These are discernable benefits you can see on the screen in a dark theater room.

It's important to understand that each of the three imaging technologies we described in Part 1 of this article deliver 4K content to the screen differently. LCoS projectors from JVC and Sony are the only home theater projectors today to offer a true native 4K-resolution array on their imaging chips, in which all the pixels of a single frame of UHD video are presented to the viewer simultaneously. Virtually all UHD-resolution DLP projectors for home theater use Texas Instrument's fast-switching pixel-shift technology, which rapidly flashes up all 8.3 million pixels in a single frame of UHD video in either two or four phases (depending on the size of the chip). It happens so fast that the eye blends these sub-frames together, and because all of the individual pixels in the frame are ultimately delivered to the screen in the right time period, it is usually difficult if not impossible to discern the difference between this and a true native 4K projector. Any difference you do see is likely more attributable to differences in lens quality or image processing.

True native 4K DLP micromirror chips are used in high end digital cinema projectors, but home theater DLP projectors acheive UHD resolution with either two-phase or four-phase pixel shifting, depending on the chip size. (Source: BenQ)

The highest-resolution 3LCD home theater projectors, all sold today by Epson, use 1080p imaging chips that are pixel-shifted once to double the number of pixels delivered to the screen in a single frame. That adds up to only half of the full UHD pixel-count. However, Epson's pixel-shifting mechanism, sophisticated image processing, and lens optics go a long way toward making the sharpness of UHD content competitive with full UHD projectors. Our tests reveal that while you can see a difference in the size of the pixels with your nose up to the screen, any difference in perceived detail is difficult to discern from normal viewing distance.

Epson's LCD home theater projectors start with native 1080p imaging chips and use an oscillating optical refracting plate to shift the entire pixel array half a pixel diagonally, doubling the number of pixels on the screen. This delivers only half of the total pixels in a frame of UHD video, but when proprietary signal processing is applied the system can effectively mimic true UHD imaging devices from normal viewing distances. (Source: Epson)

You can learn much more about pixel shifting and the different projection imaging technologies in our Tech Talk article "LCD, LCoS or DLP: Choosing a Projector Imaging Technology."

Color Gamut. A projector's color gamut describes the total range of colors available for reproduction. Most decent 1080p home theater projectors meet or come close to the full Rec.709 color gamut, which was created for high definition content. Better 4K/UHD projectors today meet or come close to the full DCI-P3 specification, which is what 4K theatrical and TV content are currently mastered to. You can see the difference most notably in more deeply saturated and natural reds when DCI-P3 content is displayed on a projector that meets the DCI-P3 color gamut spec. Going forward, UHD projectors are slowly working toward meeting the even larger Rec.2020 gamut, which is built into the UHD specification. You won't always see color gamut on the spec sheet, but 4K UHD projectors that tout "wide color gamut" will usually reproduce something larger than Rec.709, and those that promote the ability to reach 100% DCI-P3 are likely high-performing models.

Chromaticity gamut3
The dome-shaped cone in this chromaticity diagram represents the total range of colors visible to humans, while the triangles represent the range of colors reproducible by a display that meets the different color gamut specifications. Notice how wider gamuts extend further into the red and green regions, which makes everyday objects like stop signs and some types of foliage look more vibrant and natural. Today's best consumer home theater projectors achieve 100% of the DCI-P3 range used for mastering 4K HDR content

10-Bit or 12-Bit Color Depth. You won't find it on every product sheet, but color bit-depth, sometimes called color processing or video processing, is an important specification. While the color gamut determines the outside boundaries of a projector's ability to mimic colors found in real life, the color bit-depth determines how many individual colors or gradations of color the projector can recreate. This in turn determines how smoothly it can transition from, for example, the deep yellow of the sun in a sunset to the surrouning orange halo and the bluer sky beyond. If color bit-depth is insufficient, the steps of those smooth, natural transitions will exhibit noticeable banding artifacts.

The Rec.709 color standard used for 1080p content calls for a minimum of 8-bit depth, which is known to exhibit obvious banding on some types of scenes. UHD HDR content (see below) is usually mastered with 10-bit depth and shows noticeably smoother transitions. If you're buying a modern UHD projector with HDR capability, you'll want to make sure it has 10-bit or 12-bit color processing. Our article "The Deep Dive on Bit Depth" goes into detail on this subject, and also offers a downloadable, animated HDR video clip that can be used to verify whether a projector maintains 10-bit processing from its video input all the way to the screen. We run that test and report on the results in many of our UHD home theater projector reviews.

Gray Test Pattern-NoBanding

Gray Test Pattern-Banding
These two images show a 10-bit HDR grayscale pattern with little-to-no banding as it might be seen on a 10-bit projector (top) and with visible banding caused by bit-depth deficiency (bottom).

HDR Compatibility and Controls. As described above, the ability to play back HDR-compliant UHD content—and to do it well—is a significant feature that's worth paying more for in a dark-room home theater projector. Extra emphasis is placed here on doing it well. Plenty of projectors, even some 1080p models, claim the ability to recognize and play back HDR signals. But unlike with flatpanel TVs, which are inherently brighter, HDR projectors must make significant internal adjustments to adapt the content to their inherent brightness and black level capabilities. This process of "tone-mapping" gets handled differently by different projector brands, and only the best projectors do a good job, while others can leave HDR content looking flat and washed out in the dark areas, or with blown-out and unnatural highlights in the bright areas. Our product reviews always go into detail about how well the projector performed with HDR. Note that there are several types of HDR content, each requiring a compatible display. HDR10 is widely used in UHD discs and movie streams, and what we typically report on.

1080pSDRv4KHDR comparison2
UHD content mastered in HDR and shown on a capable HDR display should have wider contrast, most notably with more impactful highlights, and richer, more saturated colors due to the wider color gamut that typically accompanies HDR. Along with four times the inherent detail of a 1080p projector, HDR playback is a key reason to step up to a 4K/UHD projector. This illustration is intended to demonstrate the difference in detail, contrast, and color saturation between a 1080p image (left) and a UHD HDR image (right).

Any good HDR projector will also usually have some kind of HDR brightness control. This allows fine-tuning of the tone-map to accommodate wide variations in the mastering of HDR programs and insures a good viewing result with different movies. Better projectors usually provide a wider and finer range of adjustment, while some might only have a two- or three-position slider. Some of the very best and most recent HDR projectors have dynamic tone-mapping that monitors the incoming signal and adjusts on the fly so no extra tuning is needed. That feature is likely to become more common going forward.

D65 Color Mode. The menu in most projectors offers a choice of factory-tuned picture modes that offer different color profiles and levels of brightness. ProjectorCentral adheres to the notion that an "accurate" image follows the widely accepted production industry standards used to create the high definition and UHD movie and TV content we watch. This is the stance promoted by organizations like the Imaging Science Foundation and THX, among others—that if you want to see a picture that looks like what the creators signed off on, your home display should be adjusted to mimic the performance of their studio monitors.

Better home theater projectors will have a color mode intended to closely follow these industry-standard settings, including whites that align with the neutral-gray "D65" color temperature used for broadcasting and movies. That mode will often be labeled the Cinema or Movie mode, and will usually sacrifice some brightness compared with the default out-of-box picture mode in return for greater color accuracy. It will usually deliver the most accurate skin tones and most natural colors on everyday objects we know like foliage and blue skys. For our reviews, we use test instruments to find the best picture modes and determine their color accuracy. If you study the chromaticity diagram above in the Color Gamut section, you can see the D65 white point marked in the center where the red, green, and blue primary colors converge.

Zoom Lens. A zoom lens gives you some flexibility in projector placement by letting you fill the same size screen from a range of throw distances (that is, the distance from the lens to the screen). A fixed lens, by comparison, would require placement at a single precise distance from any given screen size. More expensive projectors tend to have longer zooms, though there is always some degree of light loss associated with fully engaging the zoom—something we report on in our reviews.

You'll see projectors noted as having a "1.2x" or "1.6x" zoom, which represents the ratio of the focal point from the widest to the longest lens position. Bottom line: more is usually better as it gives you greater flexibility in selecting a mounting location, but keep in mind that you'll likely only set up your projector once for a permanent install. If you can position the projector appropriately it may not make sense to pay more just to get a longer zoom.

Lens Vertical Offset and Lens Shift. Our Tech Talk article "Understanding Lens Offset and Lens Shift" is a great resource for understanding what can be a confusing projector specification even for experienced hobbyists. Every projector lens has a fixed vertical offset that usually makes the projected image fall somewhere above the height of the lens when the projector is resting upright on a surface. That way, if the projector is placed on a table the image will float somewhere above the projector lens where the audience can see it without any pointing of the projector that would cause trapezoidal "keystone" distortion. If the projector is inverted for a ceiling mount, the vertical offset allows it to be placed close to the ceiling and still drop the image down to fit the screen with a perfect rectangular picture.

In addition to this vertical offset, which may come into play in positioning the height of the projector in relation to the screen, some projectors have vertical and sometimes horizontal lens shift that allows you to move the entire image up/down (vertical) or left/right (horizontal). This will be given as a percent change from the default vertical offset or horizontally centered lens position. Vertical shift will likely be more valuable, as most installations allow mounting the projector square to the screen, which eliminates the need for horizontal shift.

Lens Offset-Figure 1
Lens Offset-Figure 2
Most projectors have a fixed vertical lens offset that shifts the image slightly up from the projector's resting position so it can accommodate a higher screen position without having to "point" the lens up, which creates trapezoidal "keystone" distortion. The top diagram shows the image position (indicated by the thick black line) for a 10% offset when 0% offset is defined as the lens centerline being even with the bottom of the image. If you invert the projector for a ceiling mount, as shown below, the fixed offset allows the projector to be mounted closer to the ceiling. Vertical lens shift, when it's featured in a projector, allows further range of adjustment up or down beyond the fixed vertical shift.

Powered Zoom, Shift, Focus with Lens Memory. Motorized zoom, lens shift, and focus controls accessible from the remote are a feature reserved for better and typically more expensive projectors. It's a nice convenience that simplifies setup and allows easy tweaking as needed. Powered lens control is often mated these days with storable memories that can facilitate the use of a widescreen 2.4:1 screen as described in Part 1 of this article. Whether you're watching 16:9 broadcast programming or widescreen movie content, hitting a single button will adjust these parameters to maintain a constant image height with each type of programming. Our article "When Widescreens Work: How to Pick the Right Aspect Ratio" will give you some background on this topic, but just keep in mind that if you go this route you'll be restricting your projector choices to the fewer premium models that come with this feature.

Input Lag. Input lag is an important feature for serious gamers. It describes the time delay that occurs between the moment when the projector receives the signal for a particular frame of video and when that image actually hits the screen. It's easy to understand how a long input lag would cause the onscreen image to be out of sync with a gamer's actions on the controller.

Unfortunately, input lag is often left off projector spec sheets, and is usually only mentioned for specialty gaming projectors, which tout input lag as low as 8 to 16 milliseconds. Many general home theater projectors have input lag in the 50 to 100 ms range or higher, which is suitable only for casual gaming at best. Some go as low as 20 to 25 ms, which would be considered very good among non-gaming projectors. We measure input lag and report the result for most of our home theater projector reviews.

Fan Noise. There is an industry standard for measuring projector fan noise, and you'll often see the numbers listed in a projector's spec sheet. They can be helpful for comparison, but the reality is that the numbers don't reflect the specific pitch of the noise, which can affect its intrusiveness. Most home theater projectors deliver a reasonable amount of fan noise that won't be distracting when the soundtrack is playing, but if you expect to run your projector at high altitude, typically over 5,000 feet elevation, the projector's High Altitude Mode will crank the fan much harder to keep it cool in the thinner air, and you may find it necessary to acoustically isolate the projector from viewers in some fashion. ProjectorCentral's reviews usually report on fan noise.

3D Compatibility. 3D playback of the many Full HD (1080p) 3D movie discs out there is a feature that has long been dropped from flatpanel TVs. But if you're a fan you can still select from a large group of 3D-compatible projectors and have a great viewing experience. You'll need to buy compatible glasses separately, and with some projectors, purchase a separate emitter. As with other features, it's not enough to see 3D in the spec sheet and assume it'll work well. Some projectors aren't bright enough, and some don't deliver good color in their 3D modes. Target brighter projectors in the 2,500 lumens-and-up range if 3D is a critical feature for you, and by all means, read the reviews to get an idea of which projectors are the gems and which are the dogs.


If you've now read through Part 1 and Part 2 of this How To Buy a Projector feature you should have an excellent grasp of how projectors work and what makes one better than the next. You should also be prepared to select a projector that fits the needs of your space and your own performance requirements. There's always plenty more to learn if you're a techie, and we encourage you to consult the many linked articles that will deepen your knowledge. But as fascinating as it can be to learn about the world of front projection, nothing beats the end result of immersing yourself, your family, and your friends in the thrill of that big, beautiful picture. Enjoy the journey as well as the destination, and we look forward to you coming back to ProjectorCentral often for new features and reviews of the latest cutting edge home theater projectors.

Click here to proceed to "How to Buy a Home Theater Projector, Part 1: Behind the Lens."

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