Consequently, the number of lumens present at each square foot must be reduced by four, resulting in 25 lumens per square foot. To become visible, the projected image must have sufficient light to exceed the background light. Thus, each installation has to deal with the particular conditions that exist for that screen and the normal light. In general, the more lumens produced by the projector, the brighter the screen image appears. Knowing the amount of lumens available from a projector lets you predict image visibility and identify the best size.
Native resolution is the normal resolution of the CRT monitor or laptop LCD screen.
For monitors, there are a number of possible settings, but in laptop LCD screens, the number of pixels making up the screen defines inherent resolution. You may want to think ahead about what your next computer will be and if the planned projector will handle its display resolution. Today's projectors will handle their native resolution and also usually compress the next higher level resolution. Compression uses a software program to determine the best way to display a higher resolution. Modern methods are so effective that it is difficult to tell if an image has been compressed.