The Plasma TV Blog

Put in simple terms contrast ratio is how black your display monitor makes black appear. It is often confused with brightness. Brightness is simply the intensity of the light in the images. While similar to brightness, contrast is actually the difference that exists between the brightest and the darkest part of the image. When it is measured, it is expressed as a ratio. The higher the ratio, the more lifelike the image will appear. Text printed on a computer monitor will have a contrast ratio of about 50:1, and the text on the printed page of a book might be 80:1. A good print shown at a movie theater might go as high as 500:1.

Claims have been made that some plasma displays have reached contrast ratios of as high as 10,000:1. The problem is that there is no standard method used for measuring contrast ratio, and therefore claims can be quite exaggerated. Much would depend on how the measurement is taken, and in what ambient light. Plasma televisions certainly have a big lead in contrast ratio, and this accounts for the exception clarity of their images. LCD displays have a lower contrast ratio, generally, but have greater brightness, and this brightness will be more noticeable when more light is present in the viewing area.

Once again, as in other measurements used in explaining, describing, and advertising the new generation of television technologies, contrast ratio is a useful tool for the evaluation of competing models. It must be taken with a bit of cynicism due to the inaccuracy of its measurement, and should not replace your eye as a final judge of what is best for your own home theater needs.

Pixel density, or as it is often called, pixels per inch (PPI) is a measurement of the resolution of the display of a monitor. It refers to the number of pixels in the horizontal and vertical directions of the display. It is sometimes called dots per inch, but that terminology is more accurate when referring to the resolution of a computer printer.

The terms resolution and display resolution can often be a bit ambiguous in televisions since there is such a large difference in the factors involved in older CRT displays, and the new flat panel and projection displays that utilize pixel arrays. The resolution is calculated in Plasma, LCD, and DLP technologies by multiplying the number of rows of pixels by the number of columns.

Pixel density is determined by dividing the width (or height) of the display area in pixels by the width (or height) of the display area in inches. Resolution and pixel density have applications that are important in the function of the technology. For example, in HDTV, the incoming video signal must be matching to the display monitors resolution, or converted to it. Pixel density or PPI is important in computer monitor applications when printing graphic images on a computer printer. The importance of these figures to the consumer is a little less important beyond their use in comparison shopping. Most models will include spec sheets giving pixel density and resolution figures, but ultimately the quality of the picture will be best determined by viewing with the human eye.

Shadowing is the name given to a characteristic of plasma display monitors. It occurs when a frozen image such as a task bar on a computer screen, or a static photo remains on the screen for a long period of time. The phosphor based pixels emit light continuously, and when the image changes, they are not able to quickly cease giving off some luminosity. This results in a ghost like shadowy image remaining on the screen. It appears very similar to burn in, but differs in that it is temporary, and will clear up when normal motion images are displayed on the screen.

Shadowing, like burn in, can be reduced by avoiding static images. Rotating the static image with a motion based image will reduce it, and the use of screen savers is especially effective in computer monitors. Since shadowing occurs because the pixels are shinning brightly and then are a bit slow to dim, reducing the overall brightness level of the monitor is another way to reduce the problem. When the brightness level is lower to begin with, then the shadowing problem will be less pronounced.

Remember, that shadowing is a temporary problem that has only an annoyance value, but no long term effect on your display monitor. Although it appears to be the same as burn in, and is often confused for it, it will disappear rather quickly once the static image is removed, and motion images resume, and a little caution will prevent it almost completely.

Phosphor-based electronic displays, which include both cathode ray monitor and plasma displays, are subject to a condition known as burn in. This results from a long term display of an image on the monitor. A menu bar on a computer display is a good example of the type of image that might remain on the screen constantly. Phosphor compounds tend to lost their luminosity with use, and so when certain areas of the display are used more often than other areas this loss causes a ghost like image. When it becomes visible to the naked eye, it is called burn in. This ghost image is the most noticeable effect, but more common is a continuous decline in brightness that results in a muddy picture. Plasma displays can have pronounced burn in due to the separate nature of the pixel elements.

Burn in can not entirely be prevented. The phosphor compounds are going to lose brightness the longer they are used regardless of what you do to try to prevent it. There are some things that can slow the process down considerably. Turning off computer monitors and television screens when not in use is the first step. Screen savers have been developed specifically to address this problem. The screen saver rotates the image over the full range of the phosphor display to equally distribute the load. Some plasma displays also have a process that rotates the image constantly over a small area of pixel display. This auto rotation can significantly reduce burn in, but does not really address the root problem.

Although phosphor based displays are basically deteriorating the longer they are used, the outlook on consumers is not as glum as that might sound. Most models have tested out to have quite long life spans and this is another factor that might be considered when making a purchase decision.

It was in July of 1964 at the University of Illinois, that the first prototype for a plasma display monitor was invented by Professors Donald Bitzer and Gene Slottow, as well as Robert Willson, who was still a graduate student at the time. This early monitor was developed with the idea of replacing cathode ray tubes in computer monitors because of the problems computer monitors had with refreshing rates in the display of computer graphics. The prototype display panel consisted of a single plasma cell. (The current models of plasma televisions have millions of cells.) Although still very primitive, the possibilities of plasma development as an alterative to CRT technology in television were being considered, but the advent of LCD put plasma in a holding pattern. LCD was widely used in computer monitors and then began to take the lead in the introduction of flat screen televisions.

In the next two decades the plasma display monitor enjoyed a short period of popularity. The original monochrome panels that came in mostly orange and green, with an occasional yellow screen, were in demand briefly due to the fact that they were very rugged and did not need memory or circuitry to refresh images as the CRT models did. However, with the introduction of semiconductor memory, CRT displays became much cheaper than the plasma displays. It was only the fact that plasmas could match a rather large screen to a thin profile that made them useful for limited applications, such as large screens in lobbies and the stock exchange.

Although the technology was not in the public’s eye during the 80’s, progress was being made. Such giants as IBM were interested in the technology. James Kehoe, an IBM plant manager, and Larry Weber, one of the students of Dr.Bitzer, who was involved with the original prototype, started a development company called Plasmaco. Other electronics giants were looking at the plasma process, however. In 1992, 28 years after that single celled prototype was born in an Illinois laboratory, Fujitsu introduced a 21 inch full color display monitor. The first plasma televisions were sold to the public by Pioneer in 1997. Ever since then, the screen size have been increasing. In 2006 at the Consumer Electronics Show in Las Vegas, Panasonic unveiled a 103 inch screen model.

Dr. Larry F. Weber, the Illinois student involved in Plasmaco, once said that plasma technology was a “solution waiting for a problem.” The advent of High Definition Television signals, how to bring those signals into the home, and how to display them on ever larger screens with ever increasing image quality was just the problem plasma was waiting to solve.

Link to Part 2 of this article. Plasma History Part 2

The answer to this lies pretty much within the area of personal preference and viewing habits. There is no set answer that satisfies everyone, nor is one aspect ratio so superior to the other as to make it the obvious choice. Each lends itself to certain types of viewing habits, and involves some problem when viewing items that do not have a OAR (original aspect ratio) that matches your screen.

If your viewing habits lean toward Classic Film, or older Television series, or many types of music videos, the 4:3 is a better chance as 4:3 or 1.33 is the most common OAR for these types of recorders. Many of the newer films being produced today, as well broadcasts that involve a lot of fast moving action like sporting events tend to display better on 16:9 or 1.78 screens. It is also important to note that 16:9 and its connection with HD, and its more common use with DLP, LCD, and Plasma units represents the future. At the speed in which this technology is moving, being a bit out in front might be a good idea to consider in making this decision.

You should note that both aspect ratios involve certain type of visual problems when the OAR ratio, and the actual screen ratio do not match. The window box effect of large black lines on the top and bottom of the image is a common example of this. This would be a 16:9 OAR being transmitted on a 4:3 screen. The image is spread out, and is more panoramic in its scope, but does not have the height to fill out the screen. When the smaller OAR films, like in a classic DVD film are displayed, the smaller picture might not fill the screen leaving large black borders surrounding the image. This problem is not as noticeable on very large screen units, as the resulting image is large enough making the black lines less noticeable. There are also options available to cover the lines and lessen their visual impact. This is called electronic masking, and although currently expensive does minimize this problem.

In the end it is a toss up, and your call. Be sure to take into consideration all the pros and cons and decide which ratio serves your needs best.

EDTV is short hand for enhanced definition television. The term was first applied to televisions that utilized 480p60 display resolution. The 480 referred to the vertical lines of resolution, and the letter p referred to progressive scanning. The 60 referred to 60 hertz, or a 60 cycle a second refresh rate. EDTV was basically an advertising term to counter HDTV. HDTV, or High Definition Television, was being used to describe units offering 1080I display resolution. This large increase in vertical lines of resolution was producing remarkable picture clarity, but it was still using interlacing scanning as indicated by the letter I. Interlacing scanning was presenting the image with an empty line between each line of resolution. When the next image was created, the empty lines now held the image, and the lines that had held the image became empty.

With the advent of progressive scanning, the empty lines were eliminated, and this meant that the 480p resolution when operating at a speed of 60 hertz was producing a picture comparable to the 1080I. With the popularity of the term HDTV, EDTV began to be used to denote the new technology. At the time this was done, most viewers were still finding HDTV with its 1080 lines of resolution to be a slight bit superior. This was especially true in viewing of DVDs and HD broadcast. With the introduction of 1080p display resolution, the larger number of lines coupled with the progressive scan technology was able to surpass the normal HDTV image that still used interlacing scanning. This new picture was really enhanced, but with the advent of terms such as plasma TV, DLP, and LCD TV, the use of EDTV has decreased, although this new generation of televisions were certainly worthy of the title.

A 16:9 aspect ratio is the ratio of height to length in the newer model Televisions commonly called wide screen Tvs. The first figure refers to the width of the horizontal and the second to the vertical. Most of the new generation Plasma, DLP, and LCD televisions are being offered with 16:9 aspect ratio. These new wide screen models are popular because they offer a better display of anamorphic DVD’s and HDTV broadcasts.

Although aspect ratio refers to the ratio length to width in the television screen, it also is used to denote the format of the video image itself. A video formatted to 4:3 is also known as 1.33, and the 16:9 is known as 1.78. This figure is calculated by dividing 16 by 9. Although the 1.78 is evenly matched with a 16:9 ratio screen, wide screen videos are not all recorded in a 1.78 aspect. There are several common aspects including some that are higher than 2.00. In effect, these ratios would be “too large” for the 16:9 screen, and would need adjustment, or would project an image with black lines, or some distortion. Most new films and HDTV broadcast use 1.78 or above and are very compatible with 16:9 screens.

Two other common expressions used in the discussion of aspect ratios are OAR, or Original Aspect Ratio, and MAR, or Modified Aspect Ratio. The OAR is the ratio that the video is originally filmed in, and can be adjusted by the film maker for artistic reason. The recent film Gladiator, for instance, was filmed in 2.40:1 OAR. The Modified Aspect Ratio refers to the ratio once the signal has been modified for display on a screen. Mar’s have historically been 1.33 or 4:3, but have mostly changed to 1.78 or 16:9 since the advent of HD wide screen televisions.

Aspect ratio refers to the ratio of the horizontal to the vertical size of the Television screen. The 4:3 aspect ratio screen is more of the square shaped screen. This was the common aspect ratio in the previous generation of TV and especially in CRT units

Aspect ratio does not simply refer to screen size. Video images are recorded in a variety of aspect ratios also. For example, most older and classic movie DVDs like Gone With The Wind and The Wizard of Oz come in 4:3 aspect ratio. Also, most TV broadcast signals, and all older broadcast signals that might be now available on DVD are in 4:3. This means that when they are displayed on a 4:3 aspect ratio screen with a 4:3 aspect ratio projection system, they will most closely recreate the original theatrical experience. Many music videos and concert DVDs also use 4:3 ratio aspect.

It is possible of course to show 4:3 on 16:9 screens. There are going to be certain consequences when you do this. For example, the “window box” effect, black lines that surround the picture as its aspect is expanded or contracted to adjust to the screen. It is important to remember here that the aspect ratio does not limit screen size. A 4:3 TV could have a screen 100 feet high and 80 feet long, and a classic movie on a DVD with 4:3 aspect would look pretty much the same way it did in a movie theater in 1942. It was also be viewed how the director intended it to be viewed.

In the previous generation of analog TVs, the rule of thumb was to multiply the size of the screen by 3 to obtain the distance from the TV for the maximum picture clarity. Thus, you would want to sit 12.5 feet from a TV with a 50 inch screen. The improved resolution of HDTV has caused the suggested distance to be lowered a bit. This is because the progressive scanning used to create the image has allowed the viewer to be closer to the screen without loss of clarity. The new recommended multiplier is 2 and a half times the screen size. This would make 10.4 feet the ideal for a 50 inch screen.

Calculating this optimum viewing distance and knowing the size of the room where the TV will be placed will be the limiting factor in screen size selection. It is not the only factor, however. The larger the screen, the more the unit is going to cost. So your own personal budget restraints are a factor as well. It is also helpful to have some knowledge of the technology behind the type of TV being selected, as some units are available in bigger size screens, but deliver the best quality picture at a smaller size.

Your own personal preference is the most important factor. If asked, most people would say they would like to have a bigger screen than the one on the TV they currently own, so you might as well go for the biggest screen you can afford that will fit your physical area.