Home Theater Guide

What it's all about | The Source of it all | Video Considerations | Audio Considerations | Putting it all together | Noise & Light Control

Video Considerations

SIZE

TV images have been increasing in size from the beginning. The original direct view CRT (picture tube) images were less than 10 inches. The standard picture tube grew steadily until it reached 40 inches (diagonal) a few years back. Today the largest direct view tube readily available is 38 inches. It seems likely that this is about where these sets will top out as far as image size is concerned.

Projected image size (front or rear) is limited only by light output and image resolution. Images 15 to 20 feet wide are no problem with many projectors available today, although with non-high definition sources the image resolution would dictate viewing from 30+ feet away. If you were any closer, the line structure, (or pixel resolution), would be distractingly visible - not to mention a pain in the neck, literarily from looking back and forth to see the entire image.

Several studies, as well as many years of motion picture (film) experience give us some guidelines. For maximum perceived involvement, it has been found that the image needs to occupy roughly 30 degrees of our horizontal viewing angle. Using this 30 degrees, and a given display size, we find that the viewing distance translates to just over 3 times the picture height for HDTV systems. In more general terms 2 - 3 times the image size (diagonal) is a reasonable guideline for viewing distance. Inversely the optimum image size (diagonal) is .3 - .5 times the viewing distance. This is not to say that one can not enjoy a smaller (or larger) image - just that this size range is optimum.

LIGHT OUTPUT

Light output is a major concern. If the image looks dim, or washed out, it is much harder to get involved. There is a great deal of variation in the brightness of display technologies available today. It is wise however, not to put image brightness above all else. The required level is dependent on the ambient light in the area the display is to be used. A basement room with no windows is far different then a main level great room with many windows. In many, if not most cases as the light output goes up, the image quality goes down. When choosing a display type, it is very important to consider the environment in which it will be used.

DISPLAY TYPES

There are basically 5 types of imaging devices (displays) generally available -


Choosing a flat screen - LCD or Plasma


Plasma - Pros

LCD - Pros


Choosing a rear projection TV - CRT, DLP or LCD


DLP - Pros

LCD - Pros

STEPS IN CHOOSING A DISPLAY - GENERAL