So You Want to Buy a Plasma…
You’ve been shopping around, doing your homework, and are probably more confused than ever. What is HDMI and why do you need it? What is Contrast Ratio, and why is it important? What do all those numbers mean? This is supposed to be simple, right?
Right. The trick is to cut through all the jargon, get to the meat inside the hype and spend your money effectively. This article will attempt to help you establish what the technology is, why it works so well, and what you need to expect after you open the box.
For the last eight decades or so, home video display technology has revolved around the cathode ray tube, or CRT. The CRT we’re all familiar with consists of an electron gun that shoots a focused beam of electrons against a phosphor coating on the inside of the front of the tube. The phosphor atoms are excited by the electron stream, and fluoresce, producing light.
CRTs can produce bright incredibly vibrant images. The phosphors used in CRTs produce incredibly life like colors more accurately that any display technology on the market. The only drawback is the size – they’re bulky, heavy, and take up a lot of real estate in your home.
Plasma displays use the same phosphors as CRTs, but are only 3 to 4 inches thick. As a result, they can weigh hundreds of pounds less, and take up a fraction of the floor space. You can hang them on the wall, put them in a cabinet, on a table stand, the possibilities are virtually endless. They are, effectively, the world’s most versatile picture frames.
The Breakdown, or, What’s with All Those Numbers?
Resolution: The plasma panel is made up of hundreds of thousands of glass “bubbles”, or pixels. Each pixel is further made up of three “sub-pixels”, one red, one green, and one blue. The color and shade of an individual pixel is determined by the which sub-pixels are lit up, and to what intensity. Unlike CRTs which have no fixed pixels (the actual resolution of a CRT is determined by the focus of the electron guns), plasma panels are divided into discrete pixel arrangements, 852x480 for enhanced definition models, and 1024x768 and up for high def models.
It’s worth mentioning that 1024x768, the highest resolution for 42/43 inch native “HD” displays, isn’t actually high def at all – but it’s very close. True HD signals come in three flavors, 1280x720p, 1920x1080i, and 1920x1080p (“p” stands for progressive and “I” stands for interlaced). Practically, you’ll never see the difference, but it’s worth knowing.
Brightness: The amount of light emitted by the screen, measured in candelas per meter squared. New panels will be much brighter than older panels. Like Contrast Ratio, this number is incredibly important, but also very misunderstood. Brightness ratings are often listed at 1000 cd/m2 peak white or more, but actual performance in your home will be much different. Actual brightness depends on the material you’re watching, ambient light, plasma calibration, and a host of other factors, so use this number as a general indication only.
Contrast Ratio: The most important number associated with monitor performance, and also the most misunderstood. Simply put, contrast ratio is the relationship between the brightest and darkest point of a given image. The farther apart the numbers are, the greater the detail in the darker areas. As a result, larger contrast ratios imply better picture quality.
Now, this is where it gets tricky. As of this writing, there are no standardized methods for testing and calculating contrast ratios– everybody tests and uses methods and formulae that are advantageous to their product. As a result, it’s best to ignore this number. It’s not a good indication of display performance, and won’t be until everybody starts using the same methods to test contrast performance.
Burn-in Protection: Modern plasma screens are better than ever. They look better, last longer, and are more resistant to phosphor burn. Phosphor burn, also known as image retention, has traditionally been the Achilles Heel of the plasma industry. As a result, a great deal of time and money has been spent on making plasma displays more resistant to phosphor burn.
Phosphor burn occurs when parts of the display screen “age” at a different speed than surrounding areas. Over time, the phosphors don’t react as quickly – they degrade. A number of factors contribute to this effect – watching a lot of 4:3 material on a 16:9 widescreen, station ID bugs, HUD’s in video games, etc. Now before you throw in the towel, understand that with modern units, you almost have to make a deliberate attempt to burn them.
Terminals: Think of the old real estate mantra - location, location, location. For plasma, think connectivity, connectivity, connectivity. Make sure that your plasma has the terminals you need. The sheer variety of connections out there is enough for an article all by itself, but we’ll touch on a few things to keep in mind. Firstly, whether your plasma is ED or HD, always use the best possible signal path. Plasmas will show you the limitations of your source material in a heartbeat. HDMI/DVI, on paper, is the best method of moving HD video signals, followed by component, S-video, then composite. I say “on paper” because with all the testing we’ve done we’ve yet to see any improvement with DVI over component.
HDMI/DVI - DVI and HDMI are digital interfaces for connecting digital devices, like a HD satellite box and a plasma display, for example. HDMI carries the same digital picture information as DVI, but adds several channels of digital audio as well. With a component connection, your all digital HD video signal is translated into an analog signal as soon as it leaves the box. The analog signal is translated back into a digital signal when it reaches the plasma. Imagine telling a joke in English. Translate the English to French, then from the French back to English. It’s an extreme example, but it illustrates the point: there are bound to be errors introduced with all that translation. As you can see, DVI/HDMI is undoubtedly the best format, but, my thinking is that the picture improvement over component occurs at a part of the signal that is beyond the ability of the display to show.
Component – The most prevalent connector for transmitting HD and progressive scan video. Component is an analog connection that carries the video signal in three separate parts – red, blue, and luminance. A common mistake is thinking that these cables red, blue and green picture information (they are, after all, color coded red, green and blue), but that’s not the case. Green is inferred – based on the luminance signal, what’s not red and blue must therefore be green. It’s done this way to reduce bandwidth. Component video connections can be found on DVD players, HD HT receivers, plasma and LCD displays, better CRT monitors, the list goes on and on. They don’t have to be used for HD exclusively. On standard (non-progressive) DVD players, for example, component connections are used to carry a separated video signal; luminance, red and blue picture information are kept separate, and not mashed down into a single wave form as in a composite video connection.
S-Video – Consider s-video the second worst video connection. At one time it was the best connection available for many (at the time) high end video formats, like Hi-8. It works much like component, in that the individual parts of the video signal are kept separate from each other, but this connection isn’t able to handle anything more that standard definition (D1, a.k.a. 720x486 interlaced) because of bandwidth limitations.
Composite – This is the standard yellow plug most of us have connecting our DVD players to our displays. The best you’ll get from a composite connection is 640x480 interlaced. This is the lowest quality video jack available, and not appropriate for your ED or HD plasma display.
RS-232C Interface: This port is used in the manufacture of your plasma to upload the control software and firmware. Chances are you’ll never use it, or even have to know it’s there. A service technician may access the hidden menus and controls on your display when it’s being fixed using this interface.
Getting HDTV into your Plasma
We’ve discussed the numbers, now what about making it work? What's’ with all those tuners? Below are descriptions, with pros and cons, for the various tuners available, integrated and otherwise.
NTSC – National Television System Committee – The Old Man on the block for TV standards. Your typical TV tuner that you grew up with.
Pros – Very common. More content than any other standard as of this writing.
Cons – The lowest grade video signal you’re likely to use.
ATSC – Advanced Television Systems Committee – The UHF equivalent for HD. Plug a “digital” or UHF antenna into this and you pull in free HD. Available either as a set top unit or integrated into the panel.
Pros – Free HD through an over-the-air HD antenna.
Cons – Location dependent. To determine the HD content that is available in your area please visit http://www.antennaweb.org.
Digital Cable Box – The typical set top box. Digital cable is typically QAM modulated and encrypted. The box decodes the signal, and supports a wide variety of services, including on-screen menus, channel surfing, Video on Demand, Pay per View, and others.
Pros – Full featured digital entertainment. Strong signal in any weather.
Cons – one more box to put somewhere. Not all cable providers are 100% digital.
Cable Card Tuner – A small credit card sized QAM demodulator and decryption device that slides into your plasma. Allows for HD cable viewing without the box.
Pros – No box.
Cons – no higher features, like on screen programming information, Pay per View, or Video on Demand. Simple channel changing only.
Digital Satellite Tuner – The Buck Rogers equivalent of cable.
Pros – 100% digital content, even for standard def channels.
Cons – Currently, Video on Demand not supported, although that will change.
The Bottom Line
It is my opinion that Plasma Display Panels are currently the best overall displays available. They are capable of startlingly clear, life-like pictures regardless of viewing angle. Because they use the same phosphors as CRT displays, the color accuracy is unmatched by any other flat panel technology.