Video Display Basics
Looking back over the past decade and seeing all that has transpired, one could conclude that the rate of evolution in video display technologies would have made Darwin's head spin! Today's variety of different video display technologies offers a spectrum of choices, each with a unique set of advantages. To choose the best technology for your system, consider your priorities:
Choosing the best product for your needs requires a familiarity with all the relevant technologies and all the latest product models. We recommend that you consult us early in your project. As a general guide, we've outlined some of the options below. Note that we refer to high-performance equipment; lower performance products have different profiles.
There are products in each of the above categories that have HDTV capability. However, all of the above technologies eclipse the picture quality of a traditional standard definition device, such as an old-style TV.
The choice of a screen will dramatically influence the performance of a front projection system. You can select the screen material, size, aspect ratio, and masking. The screen may be fixed to the wall or can roll down from the ceiling.
Video purists usually tend to choose constant-height screens. This means that as you switch aspect ratios from 4:3 (1.33:1) up to 2.40:1 and even beyond, the screen height remains the same. Having said that the screen needs to be matched to the room, viewing distance, and the projector—and there are reasons why a constant-height screen is not always the best for certain applications. Screen masking is another subject about which a lot could be said, but to keep things simple the goal is to mask all of the aspect ratios that you would use. Adjustable masking is desirable because that way the aspect ratio of the projected image that you are watching is bordered on all 4 sides by movable black panels, thus framing the white screen area where the image is viewed in a non-reflective black border. For a comparison of a Constant Height vs. Constant Width screen click here.
The Ultimate in Screens
For an ultra high end home theater a 4-way masking screen such as the Stewart Director's Choice can be the ultimate choice. One way of utilizing it is that it can work as a constant height screen for images from 16:9 and wider—and for images that are less wide than 16:9 the height can be increased such that a 4:3 image or a 1.37 image will not be so small compared the square area of a 16:9 or a 2.40 aspect ratio image.
Take for example a 60" constant height screen. The 4:3 image will be 60"x80" which is 4800 square inches. The 16:9 image will be about 60"x107" which is about 6400 square inches. Whereas the 2.40 image will be 60"x144" which is 8640 square inches.
Compare that to a 70"x144" 4-way masking screen, which is the same 144" width as the above. The 4:3 image will be approximately 70"x93" which is 6533 square inches. Whereas the 2.40 image will be the same 60"x144" which is 8640 square inches.
Or compare that to an 80"x144" 4-way masking screen, which once again is the same 144" width as the screen example above. The 4:3 image can be approximately 80"x107" which is 8570 square inches. Whereas the 2.40 image will be the same 60"x144" which is 8640 square inches.
Another advantage of this type of screen is that different resolutions can be projected at different image sizes. For instance because a 1080P Blu-ray has higher resolution it can be projected larger. Whereas a DVD with lower resolution can be projected smaller.
Take for example a 4:3 image from a 1080P Blu-ray which, for a certain viewing distance, might be most optimally projected as an 80"x107" size image. Whereas for example a 4:3 image from a DVD, for a certain viewing distance, might be most optimally projected as an 60"x80" size image.
For more information on the Stewart Filmscreen Director's Choice you are welcome to give us a call.
Note: This type of screen is optimally used with a high end projector that has a multitude of memory zoom and aspect ratio settings.
Perforated Screens vs. Non-Perforated Screens
The best possible audio and video fidelity is obtained if a non-perforated screen can be utilized. This approach necessitates that the center speaker be placed either above or below the screen and that the left and right front speakers be on either side of the screen. However if due to room/system constraints the only way to implement the system is to fire the speakers through the screen then the best approach would be to have selective "perfing", in which case the perfing is only in the region where the speakers are located behind the screen.
In video the aspect ratio is the ratio of width to height and can either refer to the video display hardware itself or the image as seen on the screen or video display and can be expressed in several ways. For decades the aspect ratio of the original NTSC format was called 4:3 which can also be expressed as 1.33:1 or just 1.33 for short. Now the HDTV format is referred to as 16:9. However there are many other aspect ratios than just those two. For instance over the years movies have been made in a variety of aspect ratios—and the aspect ratios of movies are usually one of the following:
Of the above the most commonly seen formats here in the US are 4:3, 16:9, 1.85, 2.35, and 2.40. Though many older foreign films are in 1.66. However a top quality front (or rear) screen projection system properly planned and setup can present all of the above aspect ratios. At this point home theaters in which movies will be viewed are typically being setup with 2.40:1 aspect ratio screens and then masking is used to present some or all of the other aspect ratios.
For a comparison of various screen sizes in terms of width, height, and square area—as well as comparing Constant Height screens vs. Constant Width Screens—click here.
General Ranges of Video Projectors & Screens
Depending on your budget and what level of performance you wish to attain, there are quite a range of projectors and screens combinations to choose from. Here are some rough ballparks of what you can expect in various general price ranges:
Video Projector Lamp Types
There are a variety of lamps used for video projection including various types of LED, metal halide, UHP, and xenon.
Many higher quality DLP video projectors use a high-pressure UHP lamp, which is also known as a mercury arc lamp. Better projectors will use a short-arc type of UHP lamp which produces a better quality of light. They are usually made with materials such as borosilicate glass and fused quartz, and because quartz is such a hard material to work with special machinery is necessary in order to heat and mold the quartz. You might be surprised to know that the glass in these lamps is not mass-produced but rather is usually hand-made by a glass-blower.
There are also some newer projectors that use LED as a light source. The advantage to using an LED design is the long-lasting nature of the light source as opposed to other light sources which occasionally need expensive bulb changes every few thousand hours. Whereas an LED light source can be give good quality light for something on the order of 30,000 hours. The challenge to using LED's as a light source has been getting sufficient brightness. However the latest designs have gotten noticeably better in this regard.
Currently the best projectors utilize a Xenon lamp assembly along with the requisite power supply and associated circuitry. One advantage of Xenon lamps that most people aren't aware of is that it only takes about 10-15 minutes for them to warm up to their optimal light quality output. Whereas UHP lamps can take 1-1.5 hours before they achieve their full optimal quality of light output. Xenon lamps can also put out a lot of light power which comes in handy for larger screens. In addition Xenon lamps inherently have a larger color gamut, also known as color space, which enables a larger range of color gradations to be seen thus enabling the most vivid, true-to-life color reproduction.
Projector Light Output Relative to Ambient Light Levels
A technically perfect viewing room would be all non-reflective black. Most people however don't have a totally dark room. If a viewing room is not totally black even a dedicated home theater without windows and with all the lights off will still have the side walls and ceiling be lit up from the light reflected off of the screen. The approach then is to make sure that there is sufficient light output from the projector for such viewing conditions such that the screen is lit up to the appropriate foot-lamberts target number. In all cases we prefer to aim for a 10:1 or better ratio between the peak white measurement from the video display device projected on the screen relative to the level of ambient light.
With regard to viewing distances relative to screen size here are some guidelines for front projection:
There is more to the story than just that though. For instance take the case of a 1080p 3-chip DLP front projector with an anamorphic lens that is used for wide screen images such as a 2.40:1 aspect ratio. Using a 2:40 aspect ratio unity gain screen which is 162" wide by 67.5" high, the minimum suggested front row viewing distance is about 2 times the screen height of 67.5" which when calculated would be a 135" suggested front row minimum viewing distance. However if an anamorphic lens is not being used and the projector can be used in the servo-zoom and focus mode then the minimum suggested front row viewing distance is about 1.5 times the screen height of 67.5" which would calculate to be about 101".
Note: the above viewing distance guidelines are for high end home theater projectors with top quality lenses coupled with high performance screens. And obviously source quality also needs to be taken into account.
Field of View
Field of View (FOV) is defined as the total angle between the viewing position and the left and right edges of the image projected on the screen. In other words this is the panorama of the viewing experience; the greater the FOV, the more immersive the experience, (for those that remember, think Cinerama). It is only recently that the technology capable of reproducing this experience was made available for residential viewing. Note that this logically applies to projector-based systems. The ideal of course is to achieve the optimal FOV, however that optimization is best done individually for a given system/room setup.
At first glance it might not seem plausible, but all things being equal a 720p 3-chip projector has noticeably more resolution than a 1080p single-chip DLP projector. The reason is that a single chip DLP has a color wheel whereas a 3-chip DLP does not. And having a color wheel reduces the perceived resolution of a video projector. Presently the highest quality projector image will come from a top quality 1080p source on a high end 1080p 3-chip DLP projector with a top quality lens shown on a top quality screen. In theory the only way to get anything better than that would be to have a source that was even higher resolution than 1080p, however as of now that doesn't exist for the home user. And there really is no point in taking a 1080p image and line doubling or quadrupling it as it will only degrade the image quality. In reality, if you look at a top quality 1080p Bluray disc on the best projector/screen setup it can be rather stunning. We know because we have it here on demo and even we are amazed at the image quality!
There are also some 4K projectors (as well as flatscreens) now available. Though, as of late 2012, 4K is now called Ultra HD (UHD or Ultra High Definition). Ultra HD has 3,840 × 2,160 pixels whereas 1080P has 1920 x 1080 pixels. However as of 2013 though there is virtually no 4K source material actually available. Hopefully there will be a variant of Blu-Ray which will provide for native 4K discs, however nothing has been announced as of 2013 anyway. Though there are some Blu-Ray players which will upconvert 1080P to 4K this is really a stopgap measure without much real merit. Until if and when high quality 4K source material is available, we are recommending sticking with 1080P for which there are a considerable amount of Blu-Ray discs available with more being released each week.
Anamorphic vs. Non-Anamorphic
One advantage to using a projector with a motorized anamorphic lens and that is movies wider than 2.40 aspect ratio can be fully masked with a constant height variable masking screen. Whereas with a non-anamorphic lens-type video projector only movies up to 2.40:1 aspect ratio will be fully masked. While there are literally only a few movies with aspect ratios wider than 2.40 available, those few wider movies will not be masked top and bottom with a constant height screen. To mask those movies with a non-anamorphic projector you would need a screen that has adjustable top and bottom masking. One reason why some people choose to forgo the anamorphic lens is to save on the price of an anamorphic lens which can be up to $15k or so for a high quality motorized one. Of course if you want to fully mask every movie made the other choice is to get a high quality 4-way fully adjustable masking screen.
If you are setting up a home theater with a video projector, one thing to keep in mind is the degree of reduction in light output when using a zoom lens—which is of course what most projectors utilize today. Depending upon where the projector is installed, the zoom lens will be in a different position from wide angle to telephoto. Understand that there are differing amounts of light output from the projector at different zoom positions—because zoom lenses as fitted to projectors aren't constant aperture, so at the telephoto end a smaller aperture (bigger f-stop) equals less light. Of course the degree of loss of light will vary from projector to projector. For example, take a 1000 lumen projector which has a zoom lens with an f-stop of 1.7 to 2.1. Dividing 1.7 by 2.1 yields a factor of 0.6553. The light output of the projector is multiplied by that factor, thus giving a 655 lumens light output which is reducing brightness by up to a third in this example.
Another aspect to be taken into consideration is how many foot lamberts a video projection system is capable of on a given screen size and material type when optimally adjusted. By the way, the best measure of brightness isn't a claimed lumens specification of a projector but actual measured foot lamberts at the screen after everything is set up and calibrated properly. In the days of film 12 foot lamberts of brightness was normal. Today many theaters are targeting 14-22 foot lamberts. For dedicated home theater rooms with good ambient light control however we find that most people prefer something in the 20-35 foot lamberts region. For a high quality front projection system we like to have a system capable of 35-40 foot lamberts, though we may adjust it down to something like 28-30 foot lamberts depending upon client preferences. It is good to have the available headroom though as a high quality projector can automatically adjust the brightness over time to account for the projector bulb getting dimmer with age so that the same level of brightness output is maintained.
Installation and Set-up
Once all of the equipment is specified, and the room is ready to receive it, the various components need to be installed. Suffice it to say that we have the necessary expertise to install your video system so that everything is properly aligned. For instance the screen should be level and at the correct height relative to the projector. And the projector should have the correct throw distance for the particular model, type of lens, and screen size. Once everything is in place then we go through an initial setup and testing procedure.
After the video system is installed and setup, the video display device needs to be calibrated. Calibration ensures that your picture will look as good as possible. To talk about calibration in depth requires using a lot of technical jargon like gamma and black level which unless you are well-versed in video terminology will probably not be meaningful to you. However to briefly touch on the subject calibration can include such things as:
Calibration itself is a specialty and there are a handful of top recognized calibration experts here in the US. Given your system and location, we will utilize the most appropriate calibration technician for your installation.
Of Course That Isn't All There There Is To It!
There are other aspects to consider as well when planning, installing, and tweaking a home theater installation. Suffice it to say that projection systems require carefully planning and implementation in order to fully realize the high performance levels that the equipment is actually capable of. Product specifications, configuration, installation, and calibration can get quite technical and involved. Of course, if you visit our showroom, we would be happy to talk to you about your home theater design and show you the stunning picture quality that we can achieve. You don't have to be an expert, that's what we are here for. In the end all you have to do is sit back and enjoy your wonderful home theater once it is installed!
NOTE: See Home Theater 3D screens for info about new developments in 3D screens.
NOTE: See Surround Audio Systems above for info on the audio portion of a home theater system.
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