Displays - Info On Which To Choose

[bazmlb]

written by a friend, prices in AUD

********************************************************************************

********************************************************************************

***************************

** Projectors are STILL! the only choice for economical big screen DVD watching. Keep your old CRT for day to day use. If you only want to have one display device, and watch stuff during daylight hours, then Plasma is the way to go for the moment. Personally, I'd wait for technology to ripen and stick to your old CRT. **

A word about aliasing:

All flat panel displays will suffer from aliasing artefacts. It is not possible to avoid this unless watching native content, or images that are evenly divisible in width and height to the display resolution. Only multisync CRTs will be free of this.

What this means:

In Australia we have 2 widescreen digital TV options: Standard Definition and High Definition.

These have varying resolutions (number of (dots) pixels high, by a number of pixels wide).

SD = 720 x 576i (interlaced)

HD = 720 x 576p (progressive) and 1920 x 1080i (interlaced)

http://www.dba.org.au/index.asp?sectionID=15

The USA (which a lot of content comes from) uses

DS = 640 x 480p (720 x 480p widescreen)

HD = 1280 x 720p

With all these formats, how do display them on a single flat panel pixel for pixel?

Well, you can't. You have to use anti-aliasing. This means you stretch and/or squash the image to fit, and this will cause artefacts. See this demo.

http://gawain.soc.staffs.ac.uk/modules/lev...html/alias1.htm

So, even though you may be inputting a 1080i image into your HDTV, your TV may not have the ability to reproduce all the dots within those lines. In this case the signal is often reprocessed (upconverted or downconverted) to conform to the number and size of dots (pixels) on the physical screen. So if your monitor is not capable of reproducing the total pixel field, then the image is scaled to fit the number of pixels in the display monitor's pixel field. So, an HDTV image of 1920x1080 needs to be scaled to fit 1366x768, 1280x960, 1024x768, 852x480, or other pixel field. The relative loss of detail actually experienced by the viewer will depend on factors such as screen size and viewing distance from the screen.

In essence, when purchasing an HDTV, it is not only important to make sure that you can input 480p, 720p, or 1080i signals, but you must also consider the pixel field of the monitor itself (and whether upconversion/downconversion is used). You want to try and avoid aliasing!

The best solution is to buy a display that has the native resolution of what you will be watching most of the time. And that changes so often! What standards will exist next year? And the one after that? Another problem here is that most devices are either manufactured for the USA market and don't fit our broadcast standards (lots are 720 x 480) or else they are using technology adapted from Personal Computers and have VGA standards (640 x 480 or 1024 x 768, or 1280 x 1024) none of which are even widescreen, or really help with our Australian standards of 720 x 576 and 1920 x 1080.

One of the few devices that can actually display an Australian HD signal is the Sony VPLVW100 which can display 1920 x 1080 natively.

http://www.sony.com.au/homecinema/catalog/...ategoryId=22033

CRT (Cathode Ray Tube) A standard TV.

This is what we are all used to. Uses an electron gun to excite a phosphor coating on the screen.

The life expectancy of CRT is a 30% reduction of phosphor brightness every 20,000 hours.

This can be compensated for by adjusting the brightness/contrast settings to a point, giving an expected useful lifetime of approx. 50,000 hours. Basically, if your television is on for 8 hours a day, its half-life would be about 15 years - or, if on 4 hours a day, the half-life would be about 25 years.

One of the problems is that the phosphors are designed to be linear, whereas the sensitivity of the human eye is not. As the phosphors fade, the eye sees more of the green phosphor due to the eye's sensitivity to green. Hence, old TVs have a green tinge to the image which most people do not notice until they compare it side by side to a new TV. (The brain does a good job of auto-white balancing.)

CRTs have very high brightness and contrast, and are capable of high resolution images.

The need for a vacuum inside the tube requires thicker glass at larger sizes making very large displays prohibitive. The largest CRT is around 100cm.

See the attached "How to set Your Monitor" for a more in depth look at CRT"

Contrast is around 5000:1 or more.

Plasma TV Overview

Plasma television technology is based loosely on the fluorescent light bulb. The display itself consists of cells. Within each cell two glass panels are separated by a narrow gap in which neon-xenon gas is injected and sealed in plasma form during the manufacturing process. The gas is electrically charged at specific intervals when the Plasma set is in use. The charged gas then strikes red, green, and blue phosphors, thus creating a television image. Each group of red, green, and blue phosphors is called a pixel (picture element).

Plasma panels have a 50% reduction (Half life) of around 30,000 hours, Basically, if your Plasma television is on for 8 hours a day, its half-life would be about 9 years - or, if on 4 hours a day, the half-life would be about 18 years.

Plasma panels have a contrast ratio of around 4000:1

Recent technology updates such as the newer Panasonic panels have a contrast ratio of 10,000 :1

Although Plasma television technology eliminate the need for the bulky picture tube and electron beam scanning of traditional televisions, because it still employs the burning of phosphors to generate an image, Plasma televisions still suffer from some of the drawbacks of traditional televisions, such as heat generation and screen-burn of static images.

LCD TV Overview

LCD televisions, on the other hand, use a different technology. LCD are now the preferred device of vendors due to their lower cost to produce. As with any technology, if more money is spent on it, it will generally prevail. Expect to see very large and impressive LCD screens in the near future.

Basically, LCD panels are made of two layers of transparent material, which are polarized, and are "glued" together. One of the layers is coated with a special polymer that holds the individual liquid crystals. Current is then passed through individual crystals, which allow the crystals to pass or block light to create images. LCD crystals do not produce their own light, so an external light source, such as florescent bulb is needed for the image created by the LCD to become visible to the viewer.

LCD panels will last indefinitely, apart from "dead pixels" due to transistor failures. The backlight however, is the limiting factor and most are rated for around 60,000 hours, Basically, if your Plasma television is on for 8 hours a day, it would last about 18 years - or, if on 4 hours a day, it would be about 36 years.

The main drawback of LCD displays is the low contrast. This makes it difficult to discern detail in areas of shadow, and even the blackest image still has a grey appearance. New technology is expected to address this.

LCD panels are also more sensitive to viewing angle. Due to the polarised nature of the pixels, contrast and brightness is lost if sitting outside the recommended viewing angle. Advances in R&D are minimising this.

LCD has a contrast ratio of 800:1 with the best available at around 2000:1

This has all recently changed. Even higher figures are soon expected.

http://www.gizmodo.com/gadgets/home-entert...-crt-180872.php

Unlike standard CRT and Plasma televisions, since there are no phosphors that light up, less power is needed for operation and the light source in an LCD television generates less heat than a Plasma or traditional television. Also, because of the nature of LCD technology, there is no radiation emitted from the screen itself.

Plasma vs LCD

The ADVANTAGES of Plasma over LCD are:

1. Larger screen size availability. This is still true with the larger plasmas hitting 60 inches, but LCDs are available up to 40 inches and both technologies have been produced to around 100 inch in prototype form.

2. Better contrast ratio and ability to render deeper blacks.

3. Better colour accuracy and saturation.

4. Better motion tracking (little or no motion lag in fast moving images). (this is now changing as current LCDs reach single figure pixel refresh rates e.g. 9ms and under)

The DISADVANTAGES of Plasma vs LCD include:

1. Plasma TVs are more susceptible to burn-in of static images.

2. Plasma TVs generate more heat than LCDs, due to the need to light of phosphors to create the images.

3. Does not perform as well at higher altitudes.

4. Shorter display life span (about 30,000 hours or 8 hrs of viewing a day for 9 years) than LCD. This can vary according to other environmental and use factors.

LCD television ADVANTAGES over Plasma include:

1. No burn-in of static images.

2. Cooler running temperature.

3. No high altitude use issues.

4. Increased image brightness over Plasma.

5. Longer display life (about 60,000 hours - at which time all you may need to do is replace the light source, not the entire set). This can vary according other environmental and use factors.

DISADVANTAGES of LCD vs Plasma televisions include:

1. Lower contrast ratio, not as good rendering deep blacks. (as stated, this is changing)

2. Not as good at tracking motion (fast moving objects may exhibit lag artefacts . - again, changing ).

3. Not as available in large screen sizes above 42 -inches .

4. Although LCD televisions do not suffer from burn-in susceptibility, it is possible that individual pixels on an LCD televisions can burn out, causing small, visible, black or white dots to appear on the screen. Individual pixels cannot be repaired, the whole screen would need to be replaced at that point, if the individual pixel burnout becomes annoying to you.

5. LCD televisions are much more expensive than equivalent-sized Plasma televisions. Still true.

Projectors:

Here is an even more diverse subject!

Apart from CRT projectors, the main drawbacks are lamp life, and brightness.

Lamp life is usually in the order of 800 - 3000 hours. Lamps cost between $300 - $800 dollars.

Brightness is not comparable to the other display types above. You need a darker room. However, the image will brighten if a smaller image is projected. This follows the inverse square law, in that an image that is twice as wide is four times as dim. So with a modern projector, you could easily display a 42 inch image in a well lit room, and then zoom out to a 100 inch image in the dark.

Brightness output of projectors is a function of the bulb and size of the unit. Projectors are available that are adequate for stadium use and other very large venues, with a price-tag to match. Brightness ranges from 700 lumens to 8,000 lumens. Hopefully, bulbs will soon be replaced with high-output solid-state lasers. This will eliminate the major weakness of a projector system.

There are three main types of projectors:

LCD

Here, the LCD panels suffer the same contrast and motion issues as LCD displays. These issues have been reduced in the last year with advancements. The use of three separate panels (RGB) allows greater brightness at added expense.

High resolution panels are available, and colour output quality of the latest generation projectors is superb.

The need to run circuitry between the pixels requires a small gap between the individual pixels that results in a fine "screen door" effect.

LCD has a contrast ratio of 700:1 with the best currently available at around 10000 :1 (with use of a dynamic iris)

CRT

These are generally considered to be the best available for colour, contrast and life expectancy. Using high intensity CRT tubes, they have a 20,000 hour operational life.

Collimating the three tubes into a single image is time consuming and thus these projectors are not portable. Which is a good thing as they are also very heavy and large.

Contrast is around 5000:1 or more. Did I mention how heavy these were? No, really.

DLP

Digital Light Processor technology uses a small, square chip that has thousands of tiny mirrors that can be angled in two directions. The tiny squares have pivots on opposite angles. Intensity is controlled by oscillating the mirrors on/off axis to create the desired light level. Because the mirrors are so close together on the chip, the "screen door" effect is negligible.

The current method of applying colour to the image is to send the output through a rotating colour wheel of RGB. This can cause some people to see "rainbow" patterns in fast moving images. This is largely addressed by increasing the speed of the colour wheels to combat visual latency.

3 panel DLP projectors eliminate this problem. I can't wait for a three panel, 1920 x 1080 laser driven DLP projector. That's where I will be!

Because the DLP reflects light rather than filtering it (as in an LCD) the contrast ratios and brightness are generally higher for a given bulb type and price bracket.

Contrast is now around 5000:1 or more.

The Future:

Two years ago I said Organic LED technology is exciting due to the fact that O-LEDS are bright, efficient, self-luminescent, and can display all colours of the spectrum from each pixel, eliminating the need to have RGB components. Current half-life expectancy is 10,000 hours. This will rapidly increase if adopted by display manufacturers as advances in manufacturing take place. .....

The technology is still great and is being used more and more for mobile phones and camera displays. The expected scalability didn't happen.

Two years ago I said - However, the price of Plasma displays is dropping rapidly as mass production and consumer acceptance grows. The race will be on to achieve an attractive price-point. (My estimate is that consumers will fork out when 150cm panels hit $2000) This may limit the development of OLED displays, but they are gaining ground in the portable device arena due to their many advantages over existing technologies (mainly resolution due to needing only 1/3 of the elements), where advances will inevitably flow into larger display technologies.

Well, the price point did drop. 42 inch plasmas for around $2000 are now common.

My new guess is that with players like Sony pushing LCD as hard as it will go, that LCD will displace Plasma in the next 12 -18 months in both price and performance. OLED will be phased in once they recoup all their R&D dollars of LCD. 5 - 7 years.

Rob Recommends:

Wait.

The big screen flat panels of 1920 x 1080 native are just not here yet.

They will be. Especially now that there are HD DVD players. http://www.dvdtown.com/hddvd/

Stick with your existing TV and buy a screen/projector for night-time DVD enjoyment. A 800x600 DLP projector will set you back $900 and throw a 100 inch image with no problem. If you want to be cheap and don't want to buy a $300 screen, use a white wall. Any image issues like colour not being quite right will soon be forgotten by the awe of the sheer size! And having to have the lights off gives you that real home theatre feel.

If you are itching to buy a big screen TV and are still confused and can't be arsed with setting up a projector, then seriously look at this for 50 inches of lovin'.

http://www.sony.com.au/homecinema/catalog/...ategoryId=23775

Can be bought for just over $3000 if you look around, and performs brilliantly. You can't buy 50 inches of this sort of quality anywhere else at that price.

If all that doesn't work for you, then just get a cheap 42inch plasma. Spend no more than $2000. You will be upgrading it in a few years time.

If you don't need or want the size, then get a quality 32inch wide-screen CRT TV!

Have more money than sense? Then this Sony projector at $14,000 is for you!

http://www.sony.com.au/homecinema/catalog/...ategoryId=22033

OLED References:

http://www.usc.edu/org/techalliance/Anthol...al_Crawford.pdf

http://www.audioholics.com/techtips/specsf...EDsdisplays.php

[udon]

I love these short posts.

How long will it be before some idiot quotes it in it's entirety?

[astral]

Long posts like this are OK in response to a specific question.

By all means let us know of technical advances, but PLEASE keep it short,

with links to the details for those who are interested.

Thanks

Astral

Moderator