Home Theater Guide
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 -
- Direct View CRT aka Standard Picture Tube Up to 38 inches diagonal
- Rear Projection (1 piece) - The most common big screen TV CRT / LCD / DLP 43 - 75 inches diagonal
- Front (Or Rear) Projection (2 piece) - Generally high end systems CRT / LCD / DLP 75 - 200+ inches diagonal
- Flat Screen - Plasma (3-4 inches thick) Newer display type 37 - 63 inches diagonal
- Flat Screen - LCD (3-4 inches thick) Newest "big screen" display type Up to 40" diagonal
Choosing a flat screen - LCD or Plasma
Plasma - Pros
- Higher contrast ratio / Better black level - Looks better in dark environments
- Lower cost for a given panel size
LCD - Pros
- Longer Life
- Higher total light output - Looks better in bright environments
- Not subject to "burn-in"
Choosing a rear projection TV - CRT, DLP or LCD
DLP - Pros
- Extremely bright image
- Higher contrast ratio / Better black level - Looks better in dark environments (vs LCD)
- Smaller overall package (vs CRT)
LCD - Pros
- Extremely bright image
- Excellent color
- Smaller overall package (vs CRT)
STEPS IN CHOOSING A DISPLAY - GENERAL
- Determine the viewing (seating) distance and calculate display size
- Make note of the ambient light in the viewing area
- Decide on the aspect ratio - wide (16:9) for movies and HDTV
- Choose a display that meets the above requirements, as well as your budget.