Color Brightness and White Brightness (Lumens)
Projectors come in a wide range of brightness which are measured in lumens. The brighter the projector the higher the lumen rating, and, all else being equal the more it will likely cost.
When shopping for a projector, be sure to look for two lumen specifications: One for color brightness and one for white brightness. There can be major differences among different projectors and brands, so color should be measured and listed separately to provide accurate information. If the information provided only gives you one lumen rating, it is typically referring only to the white brightness of the projector. The actual brightness of color may be as little as one-third of the lumens stated.
The amount of brightness you need is determined by the room you project in. Projector brightness is measured in lumens. For home theater projectors where ambient light is kept to a minimum, you'll need a minimum of 1500 lumens. For classrooms, conference rooms or rooms with windows, a projector with a minimum of 2500 lumens is best. For large auditoriums or lecture halls, you'll need more lumens.
All Epson projectors specify white brightness using ISO 21118 and color brightness using IDMS 15.4, to make it easy to compare projectors. If you are going to be projecting color images, be sure to look for a projector with high color light output.