Take into account who will be looking at your digital signage display and the environment in which they’ll view it.
Focus on factors like:
Brightness Settings: The key here is to match screen brightness to the amount of light in the area where the screen will be placed. If it’s going to be in a well-lit location, you’ll need a screen capable of supporting higher brightness settings to offset the excess light in its usage environment. Alternatively, dimmer screens are ideal for darker spaces.
Screen Size: The general rule is one foot of screen for every ten feet of room space. If, however, you’re going to be displaying any fine details (fine print, small images, etc.), consider a 1:6 ratio instead.
Viewing Angles: The quoted viewing angle for most digital signage displays is 180 degrees, though you need to keep in mind that “viewing” doesn’t necessarily mean “reading” (reading angles are often closer to 30 or 40 degrees). Viewing angles are usually tied to brightness (higher brightness levels mean wider viewing angles). Depending on where you’re going to be mounting your display (high on a wall or on the ceiling, for example), you need to factor horizontal and vertical viewing angles into your decision.