When it comes to Home Video Projection there seems to be a compromise between the amount one is willing to spend and the quality available at the right price. DLP, LCD or CRT projectors; what do these terms mean and does the latest buzz mean it is the best. We'll analyze which technology is the best for you, when it comes to selecting your Video Projection device.

DLP, LCD or CRT Projection The Best Choice For Your Needs

Richard Railey | Interactive Interiors Inc.

 

When it comes to Home Video Projection there seems to be a compromise between the amount one is willing to spend and the quality available at the right price. DLP, LCD or CRT projectors; what do these terms mean and does the latest buzz mean it is the best. We'll analyze which technology is the best for you, when it comes to selecting your Video Projection device.

by Richard Railey
Interactive Interiors Inc.


True Home Theater - is a dedicated room with insulated walls, comfy seating, a CRT projector, full screen and surround sound. Bearing this in mind, we'll explore different options to attain what your definition of a home theatre may be.

CRT - Since all true theatres contain a CRT projector, lets understand why these expensive and heavy devices are still the defacto standard for a true theatre experience.

CRT Advantages

  • Image Quality
  • 5 to 10 year lifespan
  • Clearer, Sharper and Truer
  • True black levels, can meet ISF calibration standards
  • The industry standard for HDTV
  • Handle standards above HDTV
  • Infinite Resolution
  • Runs completely quiet, no active cooling needed
  • A technology that has been proven for the last 50 years

CRT Disadvantages

  • Physical size. Large screen rear projection sets weigh up to 300 pounds.
  • Calibration required for the best picture
  • Flexible geometry, not fixed like digital displays
  • Light level is not as bright as many digital displays
  • Not recommended for still displays like computer graphics or video games.

LCD (Liquid Crystal Display) - by definition a device containing three tiny liquid crystal displays with a series of mirrors and lenses. An analog-based display technology used in video projectors, employing 3 fixed panels of pixels (one panel each for the RED, GREEN, & BLUE components of an NTSC video image). The pixels on these panels are subject to charges representing the changing video signal, the pixels orient themselves so that light striking them is either passed to a degree, or completely blocked in that area of the panel. So the panels become either transparent or completely solid; corresponding to the light & dark areas of the video image. A single light source (bulb) illuminates all 3 panels, the monochromatic images are then converged internally using a prism, and the resulting full color image is projected via a lens onto a screen. smaller - pixels there are, the better the image. On LCD spec sheets you'll see the number of pixels available quoted as "nearly a million," or 1.5 million, or more. (Because there are three LCD panels, divide the total number of pixels by three to find the pixel count on a single panel.) LCD projectors also use line-doubling technology to minimize the visible structure.

LCD projectors are very lightweight, small, relatively bright, simple to set up and operate, and relatively inexpensive due to the proliferation & usage of LCD technology in many areas.

However, the contrast range (the ratio between the whitest WHITE and darkest BLACK) of LCD projectors suffer in comparison to other technologies, because even when no light is passed by the panels, there is light present. LCD's use such a bright light source that light leaks between the individual pixels, creating blacks that appear more like shades of gray Additionally, projector bulb life is a constant investment. point to consider as well.

DLP (Digital Light Processing) -which replaces the three LCD's with a silicon chip). This technology developed by Texas Instruments, employing 1 to 3 DMDs (Digital Micromirror Devices) or chips...one each for the RED, GREEN, & BLUE components of an NTSC video image.

Each chip contains approximately 750,000 or more microscopic mirrors or pixels. Via digital input representing the changing video signal, these mirrors rapidly orient themselves so that light striking them is either reflected towards or away from a lens. Thus, areas of the chip correspond to the light & dark areas of the video image. A single light source (bulb) drives all DMDs, the monochromatic images are converged internally using a prism system, and the resulting full color image is projected via a lens onto a screen.

DLP projectors are lightweight, relatively brighter, simple to set up and operate, providing a much better contrast range (the ratio between the whitest WHITE and darkest BLACK) with higher resolution than LCD projectors. This is due to there being more surface area per mirror; less space between adjacent mirrors. The space between each mirror is approx. 1 micrometer.

Despite the advantages, projector bulb life is a consideration with DLP as well as LCD, and the DLP technology is much more expensive at present than LCD. 

Most LCD/DLP displays have picked 1080i as their HDTV standard definition. Only LCD displays are able to easily display 720p signals. For DVD viewing, a home theater monitor should be capable of displaying a 480p signal from a progressive DVD source without converting the signal to a native resolution. Since all digital displays will convert the input to their native resolution, they are not subject to this restriction. They should, however, have a VGA input that accepts a signal at it's native resolution

Even the best LCD / DLP units have a relatively low contrast ratio meaning the difference between pure white and pure black. LCD / DLP units are not able to produce a pure black and this seriously affects the final image as black is never black, more of an inky dark grey. Because of this they have less accurate grey scale tracking which affects all colours and often results in poor colour accuracy, this may be most noticeable with flesh tones which are not reproduced correctly. Beware of making direct comparisons of brightness specifications between CRT and LCD / DLP units, as CRT projectors have a much greater difference between black and white parts of an image the perceived brightness will be higher than figures might suggest.

LCD / DLP units run at extreme temperatures due to their ultra high output lamps, most actually cook them selves over time and with lamps costing substantial amounts of money and lasting relatively short numbers of hours the running costs can be higher than expected. Noise is also generally a problem simply because the use of 150-400 watt lamps in small plastic cases require serious cooling fans which make serious noise! Most CRT projectors also have cooling fans but these are thermostatic and normally only "tick over" to provide air movement in the case, there is no high output lamp burning at a constant temperature producing constant heat. LCD / DLP projectors most certainly have there uses in that they are very portable for mobile display.

LCD/DLP Digital Advantages

  • Light weight
  • Cost
  • Great for Computer Presentations and Video Games
  • Bright Colours
  • Bright display output
  • Fixed pixel based geometry
  • Easy to set up, calibrate and use
  • Allow for very large displays, up to 110" with standard models

LCD/DLP Digital Disadvantages

  • Unproven technology in the mainstream consumer world
  • Poor black level performance, many times dark pictures look washed out like the deep blacks. These are difficult to produce because the mirrors only deflect light; they don't shut light out. The resulting leakage creates blacks that are closer to dark grays. Flesh tones are not true for those who like blue!
  • Always require active cooling, some kind of fan is needed, most brands are still noisy
  • Prone to its mirror structure being visible onscreen
  • Expensive and consistent bulb replacement

Scaling new heights - A Video Line Scaler is absolutely required if using a Projector. This will significantly increases the resolution and brightness of your image, regardless of your type of display.  Some scalers work with virtually every consumer display LCD, DLP, CRT, and PLASMA. Often you gain complete control over the image, allowing exact placement of the image on your screen - you can even put a 4:3 image in the middle of a 16:9 screen! Video Scalers are also high-grade video input switchers, which allow you to match the native resolution of your display from 640 X 480 up to 1280 x 1024.


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