Thursday, February 15, 2007


The difference between display types such as LCD and PLASMA is the method or "way" used to create the picture on-screen. Each technology has it's pro's and con's as we discussed in the "HDTV 101: The Basics" section. One of the biggest issues with all the display types is "color
banding." Before I even go into this, take a look at this image courtesy of wikipedia:

The picture says it all. Doesn't it? Without even divulging into the technical aspects, you can clearly see what color banding is.

The "8 bit" and "24-bit" label refers to the number of colors. This is commonly known as "color depth" or "bit depth." An 8-bit display generates 256 colors; 16-bit, 64K colors and 24-bit, 16.8 million colors.

Whenever there are not enough colors in the pixels that make up the picture, you see the results shown under "8-bit gradient." "8-bit gradient dithered" shows a technique called "dithering" where "noise" or "random bits of information" are placed in between the pixels to try and reduce the obvious transition between colors. The result is an improvement, but overall you still have a noisy picture. By the time you get to 24-bits or almost 16.8million colors the effect of banding is reduced. Of course, this also depends on the quality of the video processing, which is why we relate to Sony, and Pioneer as top-of-the-line.

On LCD's because they work with a back light, uneven lighting of the panel can accentuate or "highlight" banding. When you first turn on or off an LCD, you can see the backlight at work before the picture comes on. This backlight is part of the reason why LCD's don't produce the best blacks; there is always light coming through even when the pixel is turned off.

The new breed of HDTV's will be looking towards producing 30-bit, 36-bit and 48-bit colors. We're talking about making a jump up to 1 billion colors. You can imagine the difference this will have on the overall picture! HDMI 1.3 will be supporting these color ranges, so expect to see a leap in picture quality over the coming months. HDMI 1.3 will allow all display types to overcome some of their previous shortcomings.


Anonymous said...

That sounds good, but actually there is no content capable of delivering such number of colors...

Anonymous said...

So, there will always be colour banding?

TriniMan said...

Good questions. HDMI 1.3 will allow this color depth possible. The video processing of the new HDTV's will determine how well this is used. We'll have to wait and see. The benefit of film is that it is so versatile. But then the camera the movie was shot on can benefit or hinder the result at home. A combination of the TV's Video processing, using HDMI 1.3, and the color timing tools used in the transfer from the post production studios will determine how the result will be. To say "there is no content of delivering such number of colors" is too broad and general of a statement. There are a lot of factors involved, with the main ones mentioned above. An example is "super-bit dvd." Remember how that came out and was 1.5 times the quality of current dvd's, but using the same equipment? Thanks for the discussion guys.