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LCD vs. Plasma Screen Displays: Technology Comparison

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Liquid Crystal Display (LCD) Televisions

Technology Overview & Description
lcd_graphic2_sm.gifLiquid Crystal Display, or LCD TVs use a florescent backlight (see LED Backlight Technologies for an update) to send light through its liquid crystal molecules and a polarizing substrate. LCD TVs work passively, with red, green and blue pixels. By applying voltage to the pixels using a matrix of wires, the pixels can be darkened to prevent the backlight from showing through. Many LCD displays double as computer displays by allowing standard analogue VGA input, a great option if you need your display to pull double duty as a PC monitor to save money and space. Nearly all LCD TVs offer flexible mounting options including walls or under cabinets.

What's Next

Thinner, bigger, faster, cheaper. Direct view LCD screens are just starting to break the size barrier that once held them back (with some models getting as large as 100+" though don't expect volume shipments) and it will be up to the manufacturing plants to convert or expand to the point where these larger screens become affordable and economical to produce. LCDs are not yet the best for black levels, but they are getting better due to LED backlighting and the "blur" effect, where the pixels cannot refresh fast enough for the screen motion, is all but extinct in newer 120Hz models.

LCD Display Advantages

  • Good color reproduction and improving contrast (high contrast tied to peak brightness capability however)
  • Very thin, getting thinner (thank Hitachi and Sharp)
  • Relatively lightweight with flexible mounting options
  • Perfect sharpness at native resolution
  • Excellent longevity
  • Among the brightest direct view displays
  • No practical screen burn-in effect
  • Silent with no moving parts or fans

LCD Display Disadvantages

  • Notorious "screen door" effect on smaller mobile displays
  • Very difficult to produce deep blacks (LED backlighting improving this)

LCD-TV_sm.jpg

Philips 42FD9954 Flat Screen LCD Display

Plasma Screen Televisions & Displays

Technology Overview & Description
plasma_lg.gif Plasma screens are basically a network of red, green and blue phosphors (each triad makes up a single pixel) mounted between two thin layers of glass. Plasma screens use a small electric pulse for each pixel to excite the rare natural gases argon, neon and xenon used to produce the color information and light. As electrons excite the phosphors, oxygen atoms dissipate and create plasma, emitting UV light. These rare gases actually have a life and fade over time.

Here's the cool part: because all the phosphor-excited pixels react at the same time, there is never any flicker apparent to the viewer. There's also no backlight and no projection of any kind, so the light-emitting phosphors, result in a bright display with a penchant for rich color and a wide viewing angle.

Editor's Note: What Are Phosphors?
Phosphors are chemical compounds on back glass that emit the visible light that makes up the picture we see. Hit them with light and they react by producing an amount of red, green or blue. On a CRT, or cathode ray tube display, the phosphors are on the front glass and are excited by a "steered" beam of electrons from the cathode-ray. On plasma monitors the phosphors are excited by UV light produced by electromagnetically charged plasma.

Plasma screens are sometimes viewed as a wonder of the modern world, and most of their attention comes from their flat presentation and large screen sizes. They are able to be produced in sizes up to 103" (don't look for mass production of this size, however) and yield a very nice picture. The downside is that they are power-hungry (not to be confused with the environmentally-friendly LCD screens). You may enjoy watching commercials with plasma screens hanging on the ceiling, but even Philips will tell you that their screens do much better hanging on a wall or placed on a stand.

What's Next

Extinction. While it has taken far longer than originally estimated, we maintain that LCD panels are on a trend to become a commodity. This year, Pioneer announced it is leaving the plasma panel manufacturing business and taking on LCD panels from Sharp. The LCD manufacturing process is getting better, additional manufacturing plants open up each year to turn out more and more panels and performance is increasingly getting better. Add to that the low cost of manufacturing and additional technologies coming on board and you have a tough road ahead for plasma. Plasma displays are indeed competing in terms of longevity, brightness, (true) contrast ratio, power consumption and burn-in. Their black levels and color saturation are very impressive. Due to these advancements it is very likely that plasma and LCD will maintain parallel development for some time. As LCD displays become thinner, cheaper, faster and more competitive, however, plasma will become obsoleted.

1080p has also finally made in-roads with plasma. Beginning with Hitachi (who unlike many other companies actually demoed a working unit at last year's CEDIA) 2007 seems to be the year of 1080p plasma technology - albeit at a price.

Plasma Advantages

  • Excellent (real) contrast ratios and black levels

  • Excellent color reproduction

  • Excellent life expectancy

  • Excellent viewing angle with no real loss of color or contrast

Plasma Disadvantages

  • Fairly heavy

  • Soon destined to be thicker than LCDs by a large margin, barring some practical technical advances
  • Susceptible to screen burn-in (new models compensate with various screen-saving methods)

  • Lower real peak brightness

  • Uses a lot of power compared to LCD

 

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