Projectors are categorised according to their ANSI lumens or brightness level.

Below 1000 ANSI lumens
These are usually entry-level projectors that appeal to those on a shoe-string budget and do not need the bells and whistles.

Output is low, so such projectors are best used in a dark or dimly lit room for small group discussions.

1000 to 2000 ANSI lumens
A step up the price and performance ladder, there are many options in this category. These projectors work best in a smaller conference room or classroom. To get the best performance from these machines, you may need to switch off a few lights in the room.

2000 to 3000 ANSI lumens
This group features the higher-end range of portable and semi-portable devices. Projectors in this group are suitable for large classrooms and big conference rooms, even a mini theatre. With higher brightness output, these projectors work fine in a brightly lit room and can illuminate a larger screen without loss of picture quality.

Above 3000 lumens
Designed for big venues like a concert hall, leacture theatres, churches and auditoriums, these projectors offer the brightest output levels. Naturally, they are more expensive.