Many A/V planners are challenged with how big large screen displays should be in their command & control rooms. There are actually some fairly complicated calculations that can be done which will help you determine what the minimum character size (sometimes referred to as ‘x’ size) should be under a given circumstance. This ‘x-size’ is defined as being the height of the smallest coherent element within the presented material. Think of this in terms of a lower-case letter x.
This lower case ‘x’ – which really is the same height as the smallest of the lower case letters – should subtend not less than 10 arc minutes on a viewers retina to be recognized at any viewing distance. This becomes more complicated when viewers are located off axis to the center of the screen as this requires a larger subtended angle and there is some affect as a result of colored symbols, amount of time the image is on screen, etc. As you can imagine… if you were sizing a screen for projection of a spreadsheet in order to go order to review your Data Center metrics you might want to use these calculations (which can be found in this ICIA publication) http://www.infocomm.org/cps/rde/xchg/infocomm/hs.xsl/9229.htm
Or a good free presentation on this subject can be found at: http://www.educause.edu/Resources/DesignStandardsandPracticesfor/155327