• Business Projectors Buyers’ Guide

    Take a look at some of the most common questions people ask while shopping for a business or presentation projector.

    How much brightness should I look for from a projector?

    The brightness of a projector is measured by ANSI lumens. DLP and LCD projectors are available at all levels of brightness to meet the needs of specific applications.

    Portable Projectors:
    Portable projectors are typically preferred by the presenter on-the-go. Micro and Ultra-portable projectors range from around 800-2000 lumens in brightness, weigh between 1.5-11 lbs, and are categorized below depending on lighting conditions.

    • 800 lumens for lights-out presentations with low levels of ambient light
    • 1000 lumens for presentations with some ambient light – this is becoming the standard brightness level for presenters
    • 2000 lumens for presentations with bright ambient light

    Projectors for conference rooms, classrooms, and similar venues

    The brightest projectors range from 2500-7000 lumens and are typically less portable. The average weights of these projectors range from between 13-30 lbs, making them ideal for more stationary conference room and classroom settings, in addition to larger audiences. Standard brightness suggestions are as follows:

    Business Projectors Buyers' Guide
    • 2500 lumens for presentations for audiences of under 100 with ambient light
    • 3000 lumens for audiences between 100-200 with ambient light
    • 5000 lumens for audiences of over 100 with bright ambient light

    How do I get the best quality image?

    Resolution 
    As a rule, the easiest way to get the best image is to match your projector’s resolution with your computer’s resolution. XGA resolution (1024×768) is currently the most common within the projector marketplace. Other common projector resolutions include SVGA (800×600) and SXGA (1280×1024).

    Uniformity 
    Uniformity represents the percentage of brightness from corner-to-corner and edge-to- edge of a projected image; the higher the uniformity rating, the better the consistency of the image. For the best images, look for a uniformity rating of 85% or more.

    What size projector do I need?

    Business and presentation projectors are now extremely portable, ranging in weights between 2-11 lbs with small footprints. If you plan to travel regularly with your projector, something within this weight range is ideal. Often times, you can find a travel case that will securely accommodate both a projector and laptop together. If your needs are more stationary or you are planning to present to larger audiences in questionable lighting conditions, you’re choice should be a larger projector (typically between 13-30 lbs) with a higher lumen output. Projectors for conference rooms, classrooms, and similar venues.

    What makes a projector easier to use than another?

    What makes today’s projectors more competitive are, in addition to their low weight and high brightness, their vast feature sets and ease-of-use.

    Newer projectors are simple to use; with strategically placed inputs and outputs and ergonomic architectures, they take mere minutes to set-up and usually require only a power outlet and a material source (such as a laptop computer). User interfaces have come a long way as well, and often mimic the look and feel of the most popular computer operating system interfaces.

    Just like current computer offerings, projectors are now typically plug-and-play and come with essential hardware options like a remote mouse, a laser pointer, or other accoutrements to simplify the life of a presenter. Portable projectors also typically ship with a standard carrying case included.

    Another added benefit: many business and presentation projectors are HDTV compatible, enabling them to tap into more presentation sources. What’s more, you can always test-drive an HDTV compatible business projector for some home theater fun!

    We recommend that you compare projector features and hardware to determine what will meet your specific application needs.

    What other features can I look for?

    There are many manufacturers that have added additional features to further simplify your presentation applications. For example, many projectors now include:

    • Wireless capabilities (options range from wireless projectors to wireless hardware accessories)
    • Network capabilities
    • Lens Shift
    • Digital keystone correction
    • Component video inputs

    Consider your specific application needs; manufacturers are taking these needs into consideration and are developing new projector solutions to meet them. We recommend that you compare projector features and hardware to determine what will meet your specific application needs.

  • Throw Ratios and Viewing Distances

    A projector’s throw ratio is defined as the distance (D), measured from lens to screen, that a projector is placed from the screen, divided by the width (W) of the image that it will project (D/W).

    Throw Ratios and Viewing Distances

    The ratio, like any ratio, is dimensionless. For example, if D equals 10 feet and W equals 5 feet, then 10 feet divided by 5 feet equals 2. The dimension of “feet” is thereby cancelled out.

    So, in knowing this formula, a projector’s throw ratio will provide you with all of the information you’ll need to set up a room. The following examples will better explain how this works.

    Throw Ratios and Viewing Distances

    Example 1: You know what screen size you want, but need to know how far back the projector will need to be placed.

    If the screen width is 7 feet and the projector’s throw ratio is 2.0 – 2.4:1 (because projectors have zoom lenses, they also have a range of throw ratios) then you can place your projector anywhere from 14 to 16.8 feet away from the screen. (7 * 2 and 7 * 2.4 = 14-16.8)

    Throw Ratios and Viewing Distances

    Example 2: Maybe you don’t know which screen size want, but you do know that the space available in your room for projector placement is limited.

    The projector should be placed 15 feet away from the screen. So, how big of a screen can you use? If your projector has a throw ratio of 1.8 – 2.22:1, your screen can be between 6.76 and 8.33 feet wide. (15 / 2.22 and 15 / 1.8 = 6.76 and 8.33)

    Viewing distance (V) is defined as the distance between your audience and the screen. A viewing ratio is V/W or the viewing distance divided by the width (W) of the screen.

    Throw Ratios and Viewing Distances

    Micro display technologies are all fixed resolution devices, hence the images are actually made up of tiny individual elements called “pixels”. If you stand of sit too close to the projected image, you will actually see the individual elements, effectively destroying the illusion of a seamless image.

    The distance from the image that you need to be, in order to view a seamless image, varies for each technology; it even varies with the resolution of the projector you are watching. Simply put, the higher your projector’s resolution is, the closer you can sit to the image.

    We suggest the following

    1. If you have an LCD projector with 600 or less vertical lines of resolution (800 x 600 or 854 x 480), a viewing ratio range of 2-3:1(V/W) is optimal. If you sit closer that two (2) times the width of your screen, you will start to see the individual picture elements, or a grid pattern known as the “screen door effect,” which gets its name by its resemblance to a screen door having been placed over the image. Conversely, if you sit farther away than three (3) times the width of the screen, the “home theater” effect will be lost.
    2. If you have an LCD projector with more than 600 vertical lines of resolution, we suggest a viewing ratio between 1.8 – 3:1
    3. If you have a DLP™ projector with 600 or less vertical lines of resolution, we suggest using a viewing ratio between 1.8 – 3:1
    4. If you have a DLP™ projector that has a resolution of 1024 x 575 or 1024 x 768, but use it only in 16:9 mode, we suggest using a viewing ratio between 1.6 – 3:1
    5. If you have a DLP™ projector that has a resolution of 1280 x 720, we suggest using a viewing ratio of between 1.4 – 3:1
    6. If you have an LCoS projector, your resolution is going to be above 720 lines, guaranteed. We suggest using a viewing ratio between 1.4 – 3:1

    We will tie together throw ratios and viewing distances in our section Setting up a Room for Front Projection.

  • High-bandwidth Digital Content Protection

    High definition digital signals pose a large problem for movie studios. If movie studios allowed equipment manufacturers to output digital images from their video sources, anyone could make a perfect copy of a film — again and again — without degradation of the image. That is the nature of digital.

    Manufacturers and studios developed a copy protection system to combat video piracy. In fact, they spent so much time developing it that the production of DVD recorders was actually delayed. When DVD players did hit the market, they lacked digital outputs and inputs, making the digital copying of DVDs impossible.

    Today, all parties have agreed upon a standard — HDCP, and we’re now seeing digital cable and satellite set top boxes with digital outputs, DVD players with digital outputs/inputs, and digital inputs on high definition televisions/monitors.

    What does this mean to you?

    All digital sources must now encrypt signals before outputting them as digital signals. This also means that all video displays must be “HDCP enabled” to decode incoming digital signals, otherwise they can’t display the images. This is very important if you have purchased a video display. Even today, many front projectors aren’t HDCP compatible, which means that you can’t use their digital inputs to watch a digital video signal.

    High-bandwidth Digital Content Protection

    Can I still watch HDTV without a digital output and input?

    Yes. For now, all HDTV set top boxes and other HDTV sources allow you to output an HDTV signal via the analog component output, just like a DVD player does. However, this is not guaranteed in the future. Although no set plan has been laid out, rumors claim that in the future, the only way to output a high definition signal will be from an HDCP encrypted digital output. And, according to rumors, all HDTV sources will be required to scale down HDTV signals to a widescreen 480i or 480p signal before outputting them as an analog signal.

    This would mean that the only way to see a true HDTV signal would be to have an HDTV enabled television/monitor. But for now, this is not the case; we will have to wait and see how everything plays out in the future.

    It is an issue to remain aware of as it would make most HDTV monitors/televisions manufactured before 2003 and 2004, and even some manufactured at later dates, useless for watching true HDTV.

    If you don’t know if your television/monitor is HDCP enabled, consult your owner’s manual or call the manufacturer.

  • 3:2 Pulldown and Deinterlacing

    Deinterlacing is defined as the changing of an interlaced image into a progressive scan image.

    Most of the newer technology display devices have some type of deinterlacer built into them, but just as in scaling, how well it is performed is critical to the image quality you see.

    Video comes to your display in two forms: video from a video camera and video produced from film. Both present their own unique challenges for a deinterlacer.

    Video originally from a video source, as in anything that would be shot by a video camera instead of film, is recorded in individual fields. (Remember, a field equals one half of a frame).

    In NTSC, these fields consist of 240 lines of information, or half the resolution needed for a full frame. The problem is that these two fields — one with the odd lines of information of the frame and one with the even lines of information for the frame — are not actually recorded at the same time.

    If everything is motionless, there isn’t a problem with simply taking the odd field and adding it to the even field, to make up one full progressive frame of information. Everything would look great. The problem therein lies with motion. If there is motion between the time the odd field is captured and when the even field is captured by the camera, you can’t simply add the two fields together to create a frame. When these fields are played back in interlaced form, one after the other, the difference in fields isn’t noticeable because they are not shown at the same time. However, if you were to simply add the fields together to form a progressive scan image, you would get something that looks like this:

    3:2 Pulldown and Deinterlacing

    Because this car is moving, just adding the two fields together won’t work. The resulting jagged edges seen above are a sure sign of poor deinterlacing and are called “jaggies”.

    A good deinterlacer will solve this by comparing the separate fields, field one versus. field two. In areas of high motion, it interpolates (averages) the two areas to create that portion of the progressive frame, while at the same time it combines only the areas that are not in motion. This process is called motion adaptive deinterlacing. The resulting image is smoothed out as follows:

    3:2 Pulldown and Deinterlacing

    You may now be tempted to say, “well, that was easy”, but hold on. We now have a new situation to consider. As we’ve mentioned before, NTSC video might have originally been converted from film. Film is, by nature, already progressive scan (a full frame), but is captured at 24 frames per second, while video is captured at 30 frames per second (60 fields per second) in an interlaced format. This means that there has to be some creativity involved in converting the progressive film into interlaced video, due to the timing difference. Here’s how it works.

    Every frame of film has to be split into fields. Two fields per frame are needed for video. The first film frame is used for the first three fields, or frame-and-a-half, of video. The next film frame is used to make the next two fields of video. This continues at a three fields, two fields rate. It looks like this:

    3:2 Pulldown and Deinterlacing

    Obviously, certain video frames don’t add up (they come from two separate frames of film), but remember that this is for display on an interlaced television. Because you never actually see a complete frame on an interlaced television, your eyes can’t see that the frames might not match up — much in the same way that motion doesn’t match up in video. This process for converting film to interlaced video is called 3:2 pulldown.

    There is a problem though. You cannot use the same deinterlacing techniques here as we used for video. What happens if we change scenes from frame A of film to frame B of film? The second frame of video would have information from two completely different scenes! You can’t simply look at the two scenes and add them together or figure out an average. You actually have to reverse the 3:2 pulldown process. Here’s a diagram of how that is done:

    3:2 Pulldown and Deinterlacing

    Looking at the diagram above, you can see that the deinterlacer first finds the original two interlaced fields that made up the first frame of film and combines them. It then displays the first full frame of film as the first three frames of progressive scan video. It does the same thing with the second frame of film, but displays it as two frames of progressive scan video. The next film frame is displayed three times again, and so on and so on.

    This works because progressive video is displaying 60 full frames of video per second instead of 60 fields of video per second. The end result is a very smooth image without any deinterlacing problems. The slight downside is that because it is displaying at a rate of three frames — two frames- three frames, the video has a slight “judder” to it. Although at 60 frames per second, it’s almost indistinguishable.

    In order to create a great progressive scan image, the deinterlacer must efficiently perform deinterlacing of both video and film. The other thing the deinterlacer must excel at is to know when it is looking at film-based material and when it is looking at video. If it can’t do that well, then everything else is rather moot, because the deinterlacer might try to render film-type deinterlacing on video (which simply wouldn’t work) and video-type deinterlacing on film (which again would exhibit serious problems).

    When purchasing a display device for home theater usage, make sure that the deinterlacer is of the best quality. Company names to look for would be Faroudja and Silicon Image.

  • DLP™ vs. LCD vs. LCOS

    The most common questions about front projectors center on the different technologies that they use. Which is better? That depends on what you are looking for. In this section will we compare the technologies as they relate to front projection. We will discuss how the technologies work in greater detail in the Learn About The Technologies section.

    Digital Light Processing™ (DLP™) — DLP™ is a Texas Instruments technology that uses micro mirrors to project an image. There are three distinct types of DLP™ light engines: three chip; single chip for home theater and single chip for business. We will cover the pros and cons for each.

    Three chip DLP™ — Pros:

    1. Perfect color accuracy.
    2. Good contrast; much greater than film theaters.
    3. Good shadow detail.
    4. Can provide high brightness compared to the limited brightness of single chip versions.
    5. Overall image quality deemed as the best of any type of micro display technology.
    6. Same technology as projectors installed in digital theaters.
    7. Pure digital technology.

    Three chip DLP™ — Cons:

    1. Very expensive compared to the other technologies. Prices start at around $20k.
    2. Lower contrast than single chip versions.
    3. Generally larger and always louder than single chip versions.
    4. Lamps usually don’t last as long.

    Single chip DLP™ for home theater — Pros:

    1. Fantastic color accuracy.
    2. The best contrast ratios and shadow detail.
    3. Generally very quiet.
    4. Very little space between each pixel creates a very smooth image, even when using lower resolution projectors.
    5. Best overall image quality available for under $10k.
    6. Very few, if any, dead pixels.
    7. Light engine failures are very rare so repairs are less costly than other technologies.
    8. Technology doesn’t degrade over time. With proper routine maintenance, DLP™ projectors consistently provide just-out-of-the-box performance. (DLP™ is the only technology that makes this claim).
    9. Color uniformity is the best of the technologies.

    Single chip DLP™ for home theater — Cons:

    1. It is more expensive than LCD technologies given comparable projector resolution and brightness.
    2. Home theater DLP’s only reach a maximum of 1500 lumens of brightness.
    3. On some DLP™ projectors, viewers can detect a color breakup effect called the “rainbow” effect. This rarely occurs with home theater DLP’s.
    DLP™ vs. LCD vs. LCOS

    Single chip DLP™ for business — Pros:

    1. Provides higher brightness than home theater DLP’s.
    2. Excellent contrast and shadow detail.
    3. Generally produces reduced noise levels.
    4. Very little space between each pixel creates a very smooth image even when using lower resolution projectors.
    5. Very few, if any, dead pixels.
    6. Light engine failures are very rare so repairs are less costly than other technologies.
    7. Technology doesn’t degrade over time. With proper routine maintenance, DLP™ projectors consistently provide just-out-of-the-box performance. (DLP™ is the only technology that makes this claim).
    8. Color uniformity is the best of the technologies.
    9. Cheaper to purchase – based on resolution and brightness – than true home theater DLPs.

    Single chip DLP™ for business — Cons:

    1. Color saturation is not as good as LCD or home theater DLP™ machines.
    2. Color separation effect, AKA “rainbow effect,” can be apparent on these projectors and can be distracting to watch, although most people don’t notice the effect.
    3. Advanced menu screens for image adjustments are rare in business machines, although some manufacturers do offer them.
    4. Most, but not all, business machines won’t offer HDCP enabled digital inputs.
    5. These machines are only offered in 4:3 aspect ratios.
    6. True 720p resolution projectors not offered.

    LCD — LCD or liquid crystal displays are the oldest type of micro display technology used in front projection. Since the only real differences between an LCD projector for home theater and one built for business are the resolution and menu options, we won’t differentiate between the two here.

    Pros:

    1. Can be very bright even in home theater applications.
    2. True high definition models are the least costly of any technologies with 720p models starting at under $2k.
    3. Great color saturation.
    4. Home theater models are usually feature-rich.
    5. 1000 lumen and lower models will usually have long lasting lamps.

    Cons:

    1. Dead pixels are common.
    2. Contrast ratios are lower than those on DLP™ projectors.
    3. Shadow detail and absolute black levels fall short of DLP™ powered projectors.
    4. Panel convergence problems (where the three LCD panels don’t align properly producing a noticeable color halo around each pixel) are common.
    5. LCD panels are organic and lose image quality over time. The less the machine is used each day, the less of a problem this is. Projectors that are used for over eight (8) hours a day can exhibit problems fairly quickly.
    6. Color uniformity across the image is lower than that of DLP™ powered projectors.

    LCoS — LCoS, or liquid crystal on silicone projectors, came along at about the same time as DLP™ powered projectors and have a much smaller market share than either DLP™ or LCD in the home theater or business machine markets. LCoS technology is also referred to as reflective LCD, while individual manufacturers use their own names. For example, JVC refers to its LCoS light engines as “D-ILA.”

    Pros:

    1. LCoS resolutions tend to start at SXGA enabling native 720p high definition images to be shown.
    2. Like LCD, LCoS machines can be very bright.
    3. Offers a very smooth, film-like image due to its pixel structure.
    4. Great color saturation and accuracy.

    Cons:

    1. Can be pricey, although based on resolution, the cost is not much more than that of DLP™ home theater projectors.
    2. Dead pixels are more visible than with other technologies and happen as often as with LCD’s.
  • Screen Types

    In this section, we’ll cover the types of screens that can be purchased, as well as the pros and cons of each one.

    Electric Screens:

    Electric screens are wall or ceiling mountable screens that use electric motors to power the screen “up and down”. Projection screens come in a multitude of styles and models, and within the electric screens there are arrays of options.

    Ceiling mount or wall mounted? Do you want the screen to mount against the wall below ceiling level? This type of mounting is common in rooms with very high ceilings. A typical wall mounted electric screen will look like the one shown in Figure 1.

    Screen Types

    Ceiling mounted electric screens come in two varieties: in-ceiling mounting and below the ceiling mounting. The below ceiling mounted screens are the same as wall mounted screens (see Figure 1), except that the in-ceiling mounted screens are made so that the opening of the screen is flush with the ceiling. These are commonly referred to as “concealed electric screens” because they are difficult to detect.

    A typical in-ceiling mounted screen will look like the one shown in Figure 2.

    Screen Types

    The last type of electric screen that we will talk about is the tensioned screen. All electric screens can be ordered tensioned or non-tensioned. Tensioned screens have a wire that runs down both sides of the screen to pull the screen fabric taut. This creates a perfectly flat surface on which to display an image.

    Non-tensioned screens can have small wrinkles and waves in the fabric that can distract the viewers’ experience. Also, non-tensioned screens are more apt to wave in a breeze of someone walking close to them, or from nearby A/C vents. A tensioned electric screen will look like the one shown in Figure 3.

    Screen Types

    Electric screens can be a great solution since they have a variety of mounting options and styles. They work great for people that haven’t yet built their viewing rooms, want a screen to be hidden when not in use, and for those with larger budgets. However, these screens are expensive, need electric outlets, and usually require structural reinforcement or remodeling of some sort to mount.

    Fixed Screens – Fixed Frame Screens

    Fixed screens are screens that are mounted to frames, very much like pictures or paintings. The fixed screen can be mounted to the frame via Velcro, lace and grommet, or snaps. See Figure 4.

    Screen Types

    Fixed frame screens are generally cheaper than electric screens and because they are mounted to frames, they are perfectly flat, making them ideal for home theater applications. However, because the screens are permanently installed, it makes concealment difficult and space must be available on walls. Also, many people find this to be a less aesthetic solution than a screen that can raise and lower.

    Manual Screens

    Manual screens are a type of roll up screen that is operated by hand. They are, by far, the least expensive type of screen to purchase. See Figure 5.

    Screen Types

    Manual pull-down screens are wall and ceiling mountable, and can be tensioned like electric screens, although not all manufacturers will tension manual screens. Like their electric counterparts, manual screens take up less space than fixed screens, but manual screens are much easier to mount. They don’t have electric motors to add weight and complexity to installation.

    On the down side, they can’t offer a perfectly flat surface like a fixed screen, and most manufacturers offer limited styles and options with their manual screens.

    Portable Screens

    Portable screens are screens that can be placed on the floor and can fold into very small packaging for portability.

    There are generally two types of portable screens including tripod screens (as shown in Figure 6);

    Screen Types

    and scissor lift screens (as shown in Figure 7.).

    Screen Types

    Portable screens are usually very limited in size and offer very limited screen surface types. Obviously the main advantage of these screens is their portability and low cost.

  • Keystone Correction

    Part 1. What is keystoning? Projector lenses are made to shoot an image above the actual projector. This enables an audience to see the image without the projector itself getting in the line of sight. For example, in figure 1, the projector is lying flat and is not tilted at all.

    If projector lenses were not made with “fixed keystone correction”, the projector’s image would land both on and off of the screen, as seen in Figure 2.

    When a projector is not set perfectly perpendicular to the screen, it will cause a distortion of the image. For example, the projector in Figure 3 is tilted upward.

    Figure 4 shows the trapezoidal image that caused by the projector being tilted upward as shown in Figure 3.

    The resulting trapezoidal image is referred to as “keystoning,” or a keystone problem. Fixed keystone correction is the ability of most projectors to shoot upwards, which makes tilting the projector upward less necessary. If fixed keystone correction is listed on a specification sheet, it will give the angle degree that the image shoots upward.

    Digital keystone correction is a function that most, if not all, projectors have that enables the user to digitally correct keystone problems when the end user is forced to tilt the projector further than the fixed keystone correction allows for. (Shown in Figure 3 and Figure 4).

    Keystone Correction

    Digital keystone correction is a function of the projector’s scaler. The projector resizes the image so that the image will appear to become square again as shown in Figure 5.

    This image manipulation is called vertical keystone correction. Vertical keystone correction also works if the reverse has happened and you need to tilt your projector downward instead of upward.

    While all projectors now have vertical keystone correction, horizontal keystone correction is much less common.

    Horizontal keystone correction is needed when the front face of the projector cannot be placed parallel to the screen surface as seen in Figure 6.

    Horizontal keystone correction will correct the image the image as shown in Figure 7.

    As a final note, we strongly recommend not using any type of digital keystone correction if it at all possible. Because digital keystone correction is a function of the projector’s scaler, it can and will produce an image with slight visual distortions and artifacts. Setting up your home theater correctly from conception negates any need for keystone correction.

  • Anamorphic DVD’s Explained

    In order to really understand this section, it is necessary to travel back in time.

    Before the VCR emerged in the early 1980’s, movies were broadcast to your television in a format know as “pan and scan.”

    Pan and scan is a technique where the wider film image is cropped off at the ends. Not surprisingly, cropping isn’t the same for each frame of film. Instead, editors viewed each film frame and decided what to cut out to convert each frame to a 4:3 image. This technique was notorious for leaving out significant amounts information, and film buffs absolutely hated it.

    Anamorphic DVD's Explained

    When VCR movies emerged, film companies initially adopted this same cropping technique, but there was an incredible backlash from people who wanted to see movie images as they were originally filmed. So as an answer, film companies invented something called “letterbox” movies.

    Letterboxed movies were VCR movies that kept the original aspect ratio of the movie by shrinking the entire image to fit into a 4:3 area. The result was a full widescreen movie, but at a much lower vertical resolution. Some people hated letterboxed movies because image details were difficult to see on smaller televisions.

    Anamorphic DVD's Explained

    Things finally began to change with the advent of DVDs. Because DVDs offered an improved horizontal resolution, television companies started offering widescreen televisions for DVDs.

    These first widescreen televisions were not high definition, but were 480i and 480p televisions with additional horizontal resolution. These televisions would take the letterboxed image and blow the whole image up to fit the screen. While this did work, it didn’t solve the problem of lost resolution. At most, the original signal would still only contain 270 lines of vertical resolution. Blowing up the signal would create a larger image, but the results were fuzzy at best.

    The solution came shortly after DVDs were introduced. New “anamorphic” DVDs were created to solve the loss of resolution.

    An anamorphic DVD is recorded differently than older letterbox DVDs. Instead of recording the DVD with black bars at the top and bottom of the image, they use the entire 480 lines of vertical resolution – if showing a 16:9 image – and use up to 364 lines when showing 2.35:1 movies, which is a staggering 25% improvement over the older letterbox vertical resolution for a 2.35:1 movie.

    How is this done? Anamorphic DVDs electronically, horizontally squeeze the 16:9 image to fit into a 4:3 area, instead of shrinking the overall image as done in letterboxing. This squeeze it a digital approximation of what would happen it you used a special lens to squeeze the image horizontally. Think of a carnival fun house mirror that squeezes your reflection to make you look thinner than you actually are. Below is an actual illustration of what an image actually looks like on the DVD, before and after your display device stretches the image back to its intended 16:9 shape.

    Anamorphic DVD's Explained

    It is important to understand is that the image recorded on to a DVD is actually distorted. You have to “tell” your DVD player what aspect ratio display device you’re using to watch the movie correctly. If you tell your DVD player that you’re using a widescreen television, when in fact you’re using a 4:3 television, you will get an image that looks like the top image of the example shown above.

    If you’re using a 4:3 television, and you “tell” the DVD player to output to a 4:3 television, the DVD player then converts the recorded image into a letterboxed image. Because it must shrink the overall image to fit onto your television, you get the same loss of resolution that you would if watching a non-anamorphic letterboxed DVD. The lesson here is that anamorphic DVDs provide no additional benefits unless you have a widescreen television to take advantage of the higher vertical resolution.

    If you do have a widescreen television, then the DVD player will output the distorted image to your television/monitor. It is then that the monitor/television electronically stretches the image horizontally into its intended correct aspect ratio of 16:9. If your television has settings for different aspect ratios, the television will have to be set to 16:9 to watch the DVD properly.

    Remember that the television or monitor will stretch the image to a 16:9 aspect ratio regardless of what aspect ratio the movie is in. This means that if the movie is in a 1.85:1 or 2.35:1 aspect ratio, you will still have black bars displayed at the top and bottom of the image.

    Most, if not all, newer DVDs that state “widescreen” are anamorphic DVDs. The back of the DVD usually will state what specific aspect ratio the movie is in, although some companies still refuse to put that valuable information on their DVDs.

    Labels identifying anamorphic DVDs often appear as shown in the example below, however anamorphic DVDs are not always clearly marked as “anamorphic.” You can assume a DVD is anamorphic if the DVD packaging reads “widescreen version” anywhere on the front or back covers.

    Anamorphic DVD's Explained

    Progressive scan DVD players

    Newer DVD players have the ability to output signals as either interlaced or progressive scan images.

    Generally, when film is converted to DVD, 3:2 pulldown is applied so that the DVD player can output an interlaced 480i signal. During the encoding of the DVD, the original two fields that make up a specific original film frame are flagged so that, if played on a progressive scan DVD player, the DVD player can easily convert the film into a progressive scan image.

    There are a few things to note about progressive scan DVD players:

    1. Once you output a progressive scan image, the signal is no longer an NTSC, or 480i signal. It becomes a 480p signal – p for progressive scan. If you don’t have a television that can input a progressive scan image, you will not receive an image. (Note: Turning an interlaced image into a progressive scan changes the refresh rate from 60 fields per second to 60 frames per second, which is double the information per second. A television must be designed to handle that extra information.)
    2. A progressive scan DVD player will only output a progressive scan image via its component video, or digital video outputs. If you use the S-video or yellow composite type output, your television/monitor will only receive a 480i image. S-video and composite cables will not accommodate a high enough resolution to carry a progressive scan image.
    3. If you are watching a non-film based movie, the image may worsen if you output it as a progressive scan image.
    4. The built in deinterlacer of a progressive scan DVD player is very important to video quality. And, you get what you pay for. More expensive progressive scan DVD players will have higher-quality deinterlacers built in that can distinguish between film based-material and video. They adjust automatically for the best image quality possible. Also these higher quality deinterlacers will better handle video-based material without video artifacts common to low-cost deinterlacers.
    5. All HDTV monitors/televisions will be able to handle a 480p signal.
  • Plasma Displays Pros and Cons

    Pros:

    1. Plasma displays are very thin. They can be mounted in places traditional CRT televisions and monitors cannot.
    2. Color reproduction is excellent.
    3. Contrast is good, although not great.
    4. Plasmas are now manufactured with screen sizes as large as 70″ diagonal
    5. Enhanced resolution display prices rival the prices of rear projection televisions of similar size
    6. High definition resolution (HDTV) displays are much less expensive than LCD flat panels of the same size.
    Plasma Displays Pros and Cons

    Cons:

    1. Fragile technology; doesn’t ship well.
    2. Black levels and detail in dark scenes are not as good as CRT or DLP™ powered rear projection televisions.
    3. Dead pixels can be an issue, although quality has improved as the technology has matured.
    4. They are a phosphor-based technology, which means that burn-in of an image can occur, and that the display’s image quality will diminish with time.
    5. Cheaper enhanced definition (EDTV) plasma displays have rather large pixel structures.
    6. Plasma displays are very heavy and usually require wall-strengthening for wall mounting.
  • Liquid crystal on silicone

    (a.k.a D-ILA, SXRD and Reflective LCD)

    Liquid crystal on silicone (LCoS) technology has a few variances that are in the market place; JVC calls its version D-ILA, while Sony has named its version SXRD. Nonetheless, all versions work in pretty much the same manner.

    Think of LCoS technology as an LCD on a silicone wafer. To build on that, let’s start with how a liquid crystal in a LCoS panel works.

    Polarized light is first sent to the LCoS panel. Think of the polarization process as a filter that only accepts light waves that are all traveling on the same plane. In this way, if you were to put two polarized filters back-to-back that filtered the light in opposite planes, all of the light would be blocked from passing through.

    This polarized light travels to the LCoS panel and passes through a pane of glass and transparent electrode to the liquid crystal inside.

    Liquid crystals have the unique property of bending light as the light travels though them. In this manner, the polarized light leaves the liquid crystal, actually traveling on an entirely different plane that when it entered. In the case of an LCoS panel, the light is reflected off the silicone layer behind the liquid crystal and back out of the front of the LCoS panel.

    If you apply current to liquid crystal, the crystals align themselves and will not bend the light. Instead, the light leaves the liquid crystal on the same plane that it entered.

    If you align a second polarizing filter to filter the light that was reflected through the LCoS panel, you can block all light from escaping if the light waves are traveling on a plane that the filter blocks. See Figure 1.

    Liquid crystal on silicone

    Now we can talk about how the panels are used in an optical engine to produce and image.

    An LCoS optical light engine incorporates three small LCoS panels (AKA SXRD or D-ILA panels; see Figure 2.), a lamp, filters and prisms to create an image.

    Liquid crystal on silicone

    White light is provided by way of a lamp. The lamp light is first passed through a dichroic mirror (a mirror that reflects only certain wavelengths of light while letting all others pass through) that splits the white light into yellow and blue light.

    The yellow light is then passed on to an additional dichroic mirror that splits the yellow light into red and green light.

    The red, green and blue light is then passed through polarizing filters before being sent to directional prisms that reflect light coming from a certain direction, but allow the same light to pass through if coming from a different direction. These prisms are used to bounce the light off of the three LCoS panels.

    After the red, green and blue light is bounced off the LCoS panels, it is sent to another dichroic prism, which recombines the three primary colors. After the three colors are recombined, the light is passed through the main lens and out of the projector. See Figure 3.

    Liquid crystal on silicone

    Each LCoS panel controls one of the three primary colors. For example, if we were to show an image of an open green field with a blue sky, the LCoS panel that controls red would block all light from passing on to the dichroic prism, while the LCoS panel that controls blue would only allow blue light through for the areas of sky. Meanwhile, the LCoS panel for green would do the same for the areas of the green field.

    Each LCoS panel has individual cells that are each controlled by a separate transparent transistor that can apply current to the liquid crystal within the cell. The resolution of the display determines the number of cells, or pixels, that the LCoS panel has.

    In this way, each panel can control what color each pixel is going to be at any given moment. If a pixel needs to be white, all three panels let through light at their corresponding pixel, and the three primary colors are recombined by the dichroic prism to create white light.

    All pixels working together in the projector can then paint a picture in much the same way a printer uses individual dots to make a color image on paper.

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