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Home Cinema Buyer's Guide
Aspect Ratio
 
When we talk about 4:3 and 16:9 formats we're talking about the rectangular shape of the video image, or what is called its aspect ratio. A standard TV has an aspect ratio of 4:3. That means the picture is four units wide for every three units of height. The HDTV standard is 16:9, which is 16 units of width for every 9 units of height. So HDTV's 16:9 is horizontally wider than regular TV, which by comparison looks almost square.

Here's the problem: any given projector or TV comes in its own native format--typically either 4:3 or 16:9. On the other hand, movies and video come in many different aspect ratio formats. TV programs and videos intended for regular TV are done in 4:3 format, often denoted "1.33:1" since 4 divided by 3 = 1.33. On the other hand, programs made for HDTV are in 16:9 format, which is 1.78:1 (16 divided by 9 = 1.78).

However, these are not the only two formats that video material comes in. Movies, music videos, and other content on DVD comes in a variety of formats including 1.33, 1.78, 1.85, 2.00, 2.35, 2.4, 2.5, and so on. So there is no universal standard for the rectangular shape of a video picture. But one thing is clear: no matter which format projector you get, either 4:3 or 16:9, it will NOT fit all the video material you will want to watch in its native frame. Since there is no perfect solution, what is the right way to set up your system?

The most popular choice for a home theater system is to go with a 16:9 projector and a 16:9 screen. But some people still like the more classic format of a 4:3 projector with a 4:3 screen, since all classic films prior to 1953 were made in this format. And today there is a lot of interest in dedicated super-widescreen 2.35:1 systems as well. Each of these three configurations offer some unique benefits, as well as some disadvantages that should be considered before taking the plunge.

Aspect Ratios: Benefits and Downsides
  • 4:3 Theatre

    Advantages: If you want to view material such as classic films, or DVD-based television series like Friends or Northern Exposure, or an IMAX special like Everest in very large dramatic format, the 4:3 set-up lets you do this in a way a 16:9 system does not. Using vertical electronic masking, one can easily block off the top and bottom of the screen when one wishes to display 16:9 or 2.35:1 material, and open the screen to it's full vertical height for the viewing of very large format 4:3 material.

    Disadvantages: Most high quality home theater projectors being marketed these days are in native 16:9. As such, it can be hard to find a 4:3 projector that delivers great video that rivals the quality of the 16:9 home theater models. And since most 4:3 projectors are in resolutions such as 800x600, 1024x768, and 1400x1050, it means that all video content will need to be scaled to fit the projector's native resolution.
  • 16:9 Theatre

    Advantages: For HDTV and widescreen DVD, 16:9 is the logical choice. All HDTV broadcast material is in 16:9, and it will be displayed in its full glory, without black bars, on a native 16:9 projector. And there is a lot of 16:9 programming available. There are many 16:9 projectors to choose from, and many of them are designed specifically for high quality home theater.

    Disadvantages: While 16:9 programming looks larger than life, 4:3 material displayed on a 16:9 projector can appear downright tiny. Generally it is centered on a 16:9 screen with black columns on each side. With broadcast 4:3 material the side columns framing the picture can be medium gray instead of black, which looks terrible. Projectors generally have some horizontal stretch options to force a 4:3 picture to fill a 16:9 frame, and if you are not concerned much about the quality of your 4:3 viewing, this can be a worthwhile compromise.

    Alternatively, if you watch a lot of movies that are wider than 16:9, you will have black bars above and below the image. A masking system can be used to close the screen's active surface area to fit the format of the movie you are viewing. This makes the picture look better, but it adds cost to your system. If you don't want to go through the trouble of purchasing and installing a masking system, you'll need to live with black bars for content that is not 16:9.
  • 2.35:1 Theatre

    Advantages: Many movies are wider than 16:9. For example, Seabiscuit, The Lord of the Rings, Dances with Wolves, Tombstone, U-571, American Beauty, and Star Wars/Phantom Menace are all 2.35:1, not 1.78:1. If many of your favorite movies are in 2.35:1, then a 2.35:1 constant image height (or CIH) setup is a good choice. This entails purchasing a 16:9 projector and using a separate, external 1.33x anamorphic lens to stretch the image out to 2.35:1 (1.78 multiplied by 1.33 is 2.35). To view 16:9 and 4:3 material, you must move the anamorphic lens out of the light path. But a set up like this can deliver the ultimate in widescreen drama.

    Disadvantages: Anamorphic lenses are not cheap, and can add thousands to the cost of your theater. Also, you must be able to move the anamorphic lens into or out of the projector's light path as you switch between 2.35 films and 16:9 or 4:3 material. Motorized mounts make this easy but add cost to the system. Cheap anamorphic lenses can impair image quality somewhat. You may also want to include an electric masking system to close the screen from the sides when 16:9 or 4:3 material is being viewed. This makes it look better, but again adds more cost to the system

Brightness
 

How much illumination your eyes perceive on the screen depends on two factors: (1) the light output of the projector, and (2) the reflective properties of the screen.

There are two common methods of measuring light in a home theater. One is the ANSI lumen rating of the projector. That measures the light energy capable of being generated by the projector itself. The second is foot-Lamberts (fL), which takes the screen into account and measures the total light that is being reflected back toward the audience. Of the two, foot-Lamberts is the better method to use for setting up your home theater. However, since that number depends on your screen size and screen gain, there is no fL specification published by the projector manufacturers.

So how much light do I need?

When it comes to home theater projectors, brighter is definitely not better. What you want is a projector that produces enough light to fill your screen with good contrast, but not so bright that it creates eye fatigue when viewed for any length of time.

It is safe to ignore the published ANSI lumen rating—it is irrelevant for a variety of reasons. In a dark room, a luminance level on the screen in the range of 12 to 22 fL is in the ideal comfort range, and the calculator defaults to 16 fL to give you a starting point.

In theory, lumens and foot-Lamberts are related—one foot-Lambert of luminance is equal to one lumen per square foot. But there is no direct relationship between the ANSI lumen ratings from the manufacturer and the foot-Lambert measurements as reported in the Calculator. That is because the Calculator factors in reduced lumen outputs for video optimization and average lamp usage, in order to estimate a typical viewing experience.

If you don't want to set up a dark home theater and would rather have some low ambient light, many users prefer to get the screen luminance up into the range of 30 to 50 fL. A brighter picture will help compensate for the loss of contrast caused by the ambient light. For each model you may be considering, the Calculator can be used to give you estimates of the screen size and screen gain needed to get that brighter picture.

Don't Get Misled by ANSI Lumen Specs

Whatever you do, don't make any assumptions about a projector's brightness based on its ANSI lumen rating. Some models have video optimization incorporated into their ratings and others do not. That means there are projectors out there which are officially rated at 700 ANSI lumens that are actually brighter than models rated at 1500 ANSI lumens. So the spec sheets, as far as lumen ratings are concerned, tend to be meaningless for home theater.



Contrast Ratio
 

Contrast is the difference in brightness between maximum white and deepest black in an image. The greater the difference, the higher the contrast.

Why is Contrast so important?

With business projectors, lumen output is of primary importance, and contrast is a secondary concern. Home theater projectors are the exact opposite. Contrast is arguably the single most important measurable quality in a home theater projector. A high contrast projector produces a picture with a rich, dynamic look, good shadow definition, and deep color saturation. Contrast gives "depth" to video images. A projector with excellent contrast can make a two-dimensional image appear almost three-dimensional.

Contrast Ratios

The contrast ratios noted on a projector's spec sheet can be reported in one of two ways. If it just says "Contrast," it usually indicates On/Off contrast, which is the ratio of the whitest white and the darkest black that the projector is capable of producing. If it says "ANSI contrast," the ratio has been determined by displaying a checkerboard pattern of white and black squares and measuring the relative brightness of each. On/Off contrast is always a larger number, and more typically listed on projector spec sheets, but ANSI contrast is a more accurate representation of what your projector is actually capable of during normal use.

Typical Contrast Specifications

Some typical On/Off contrast figures for home theater projectors are as follows:
  • 2000:1

    There are many entry-level projectors rated at 2000:1 on/off contrast. 2000:1 is typically enough to give satisfying black levels and color saturation, enough to avoid the sense of flatness or muddiness in a picture.

  • 5000:1

    Projectors rated at 5000:1 are usually capable of better blacks than 2000:1 projectors, and shadow details are better defined. In today's market, 5000:1 represent the midrange of performance for good home theater projectors.

  • 10000:1
    As of this writing, if you want the best contrast that money can buy, you want a projector rated at 10000:1 contrast or higher. These projectors offer deep, inky black levels and excellent shadow detail that should be sufficient for even the most demanding content.

What about a dynamic iris?

A dynamic iris is a device built into some projectors that sits between the lamp and the lens. Many times per second, the projector evaluates the overall brightness of the image being projected at the moment, and then opens or closes the iris to allow more or less light through.

A good dynamic iris will improve on/off contrast. Dark scenes will appear darker, while bright scenes will appear brighter. The contrast ratings will be based on the whitest white with the iris opened, and the blackest black when the iris is closed. That means that the projector will never achieve the rated contrast in any given scene. From a practical perspective, a projector that has no dynamic iris and is rated at 3000:1 contrast may actually appear higher in contrast to the eye than a projector rated at "up to 10,000:1," but with that rating based on its dynamic iris variations.

So once again, as with the ANSI lumen ratings, it is best to take official contrast specifications with a grain of salt. They can be highly misleading.

Dark Room Needed for Best Results

You've noticed that commercial movie theaters are dark, including dark ceilings and walls. That is because any front projection system looks its best when there is no light in the room. Once you introduce ambient light into the room, that light will hit the screen and make blacks look more like dark gray. This reduces the contrast of the image, and makes it look flat or washed out. And this will happen no matter what the contrast capability of your projector is.

Though the ideal viewing room is dark, most people don't want to darken the walls and ceiling of a living room or multipurpose room just to get ideal theater conditions. Today's high contrast gray screens help to hold black levels solid when there is some ambient or reflected light bouncing from light colored surfaces in the room back onto the screen. But for the best possible image quality for any home theater, take whatever steps you can to eliminate ambient light and reduce the reflectivity of the room's walls and ceiling.

     
Installation
 

The best projector on earth is useless if it doesn't fit in your theater. To make projectors easier to fit in to a variety of rooms and help them accommodate different screen sizes, many projectors now incorporate zoom lenses and physical lens shift.

Zoom Range

A zoom lens is able to make the projected image larger or smaller by shifting the internal optical elements of the lens. This allows a projector to deliver the desired image size from a range of throw distances. Some projectors have a very limited zoom range. For example, a 1.20:1 lens, sometimes noted as 1.2x, means the maximum image size is just 20% larger than the minimum size. On the other hand, some projectors have zoom lenses of 2.0:1, or 2.0x, meaning that the maximum image size is double that of the minimum image size. Such a lens provides a lot more flexibility to create the image size you want from the place you want to locate the projector.

Though long zoom ranges offer great flexibility, the projector's potential light output usually drops somewhat if you use the telescopic end of a long zoom lens. So if you want to maximize light output, it is best to avoid the longest throw distance the lens will allow.

In your search for the right projector, first determine the size of the image you want on the wall. Then use the Projection Calculator to see if the model you are looking at will create that size image with the room size and throw distances you have to work with.

Lens Shift

Another feature that makes installation easier is lens shift. The ability to move the lens up or down, left or right, while keeping the projector stationary lets you change the location of the projected image on the wall. This makes it a great deal easier to place the projector where you want it, and adjust the lens so that the image fits your screen perfectly. If you do not have any lens shift capability, you will need to take extreme care to position the projector at the precise location demanded by its fixed throw angle.

If the projector does not have lens shift, one alternative is to tilt the projector such that the image fills the screen from the position you want to place the projector. However, this will result in a trapezoidal shaped image. You can square it up using keystone correction, but this is something you should avoid if possible since it can soften the image a bit.

Vertical lens shift moves the image up and down, which allows the projector to be placed at different heights and still properly light up your screen. The range of shift varies by projector, anywhere from a modest range of half a screen height, to a typical maximum of about three screen heights. If you plan to install your projector on a rear wall so that the projector is about the same height as the screen, you only need a modest lens shift range. On the other hand, if you plan on ceiling mounting your projector and having it throw the image downward to the screen, a more extensive vertical lens shift range is required. Without lens shift, it is sometimes possible to ceiling mount the projector in the precise location dictated by its fixed throw angle. However, this often requires the use of a drop tube to distance the projector from the ceiling while maintaining your preferred screen height.

Horizontal lens shift moves the projected image from side to side, which enables the projector to be placed off-center from the screen. While horizontal lens shift is not normally as extensive in its range as vertical shift, it does allow for some movement, which is crucial if you cannot place your projector in line with the center of your screen. Horizontal lens shift can vary between 5% and over 50% of a projected image's width, and it is much less common than vertical shift. In order to illuminate a home theater screen evenly, the projector should be as close to the center axis of the screen as possible.

The availability of vertical and/or horizontal lens shift on a given model is noted in ProjectorCentral's database, but the specific range data is not. However, these specifications are always discussed in ProjectorCentral reviews. They can also be found in the Owner's Manuals, many of which are online. When they are available, you will find a link to them from each model's specification page in the database.



Resolution
   projector's resolution (or more precisely, its "native resolution") is simply the number of pixels that it has available to create an image. The higher the resolution of a projector, the more pixels it has.

Projector resolution is designated with two numbers, such as "1280x720." The first number indicates how many pixels there are in each horizontal row, and the second number is how many pixels make up each vertical column. If you were to multiply the two numbers, you would end up with the total number of pixels on the display device.

Generally speaking, the higher the resolution, the more the projector will cost. The advantages of higher resolutions are that (a) they can display more detail in the picture (assuming the video signal has the detail in it), and (b) they reduce or eliminate the visibility of the pixel structure. Both of these are highly desirable in good home theater. The advantage of low resolution projectors is that they cost so little, so you can get into large screen home theater with a small investment.

Common Resolutions in Home Theater Projectors

Projectors come in a variety of different resolutions, including the following:
  • 854x480: This is the least expensive and lowest resolution on the market. It is designed for optimum display of standard definition material in NTSC countries, since both NTSC television signals and standard DVDs contain 480-lines per frame of video. An 854x480 projector can display 480-line video without any vertical scaling, so the picture will look its sharpest. If you live in an NTSC country, you watch primarily DVD and television, and want to get a good basic projector for the least cash outlay, the 854x480 models may be just right for you.
  • 1024x576: There are few projectors in this resolution these days, but you can still find them on the used projector market. They were designed for optimum display of PAL/SECAM video, which contains 576 lines per frame. They have little practical use in NTSC countries. But if you live in a PAL or SECAM country, these can be inexpensive alternatives that are ideally suited to viewing standard definition PAL/SECAM video.
  • 1280x720: This is currently the most popular home theater projector resolution on the market. Most 1280x720 projectors offer very good to excellent DVD video quality. In addition, they have the unique advantage of being able to display HDTV 720p in native format without scaling. They also do a beautiful job of displaying 1080-line video; even though the signal is compressed into its 720-line format, it still comes out looking like true high definition. Street prices on the most aggressively priced models have dropped below $1,000, so this excellent resolution format is easy to get into from a budget perspective.
  • 1280x768: This is a hybrid resolution that combines the ability to display 16:9 video in 1280x720, as well as standard computer resolutions XGA (1024x768) and WXGA (1280x768), in native form without scaling. If your viewing material includes both video and computer data or Internet surfing, this format will allow you to see the computer data signals in their clearest, unscaled form. Note that this is a 15:9 aspect ratio rather than 16:9 as are the others in this list. So when you are viewing 16:9 video material, there will be small black bars at the top and bottom of the projected image. That is the penalty you pay for having those extra 48 lines available to accommodate XGA computer signals.
  • 1920x1080: The ultimate high definition format, and also the most expensive. The key advantage to this resolution is that it will display HDTV 1080i signals, as well as 1080i and 1080p signals from HD DVD and Blu-ray disc players, all in native format without any scaling. This gives you the sharpest and most detailed images available today. Due to the pixel density, visible pixel structure is virtually non-existent

Selecting the right resolution for you

We currently recommend two resolutions for widescreen, 16:9 format home theater, those being 1280x720 and 1920x1080. If you want your projector to double as both a video and data projector, the 1280x768 format should be considered as well.

The 1280x720 format is the best choice if you have a more modest budget and/or you don't want to pay a large premium to get the absolute maximum detail out of a 1080i or 1080p video signal. Today's 1280x720 projectors (often referred to in shorthand as "720p projectors") deliver beautiful high definition images from HDTV 720p, 1080i, as well as HD DVD and Blu-ray disc players, so there really is not much of a compromise in picture quality by going with 1280x720 instead of the higher resolution 1920x1080 format.

On the other hand, if you have the money to spend, and you want the absolute sharpest and most detailed picture possible from high definition sources, then 1920x1080 projectors (commonly referred to as "1080p projectors") are the best choice. While the 1280x720 projectors can deliver very impressive HD images, the picture quality in terms of image detail is even better when the projector has the ability to show all 1080 lines of the signal in their native, uncompressed format.


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