Video Asylum

Posted by David Aiken (A) on April 03, 2007 at 02:33:24

In Reply to: Re: please explain posted by michael w on April 2, 2007 at 21:38:46:

A Video Standard and Video Essentials have now been superseded by Joe Kane's Digital Video Essentials which looks a little at more modern display types.

DVE re-iterates the recommendation that CRT screens be placed in front of the wall but doesn't specify the distance in front. It gives 2 reasons for this, first the desirability of placing an ambient light behind the screen, and secondly because it allows the eye the opportunity to focus on the wall which, being further away, provides some relief from the strain imposed on the eye of focussing on the screen. It does not specify whether the effort of close focussing or the strain of looking at a relatively bright screen is the major cause of eye strain when focussing on the screen.

There are screen types, like front projection screens, which are placed on the wall and for which DVE does not recommend placement in front. DVE comments that ambient light degrades the picture quality with front projection screens and recommends that the room be kept dark. In a dark room, wall location does not matter since it can't be seen anyway.

Flat screen displays like plasmas and LCD screens are also sensitive to ambient light levels and do better in darker rooms. LCDs hold up better to ambient light levels than do plasmas which are better in a dark room, but LCD screens still benefit from darker rooms. If you're setting up the screen for optimum picture quality and you are darkening the room, where the wall is located in relation to the screen isn't going to be critical because the wall won't really be seen anyway.

I think this fact, low visibility of the wall rather than screen size, is the reason why wall placement is less of an issue with flat screen displays.

David Aiken