High-end and large venue projectors are sometimes sold both with or without a lens. The manufacturers usually offer several optional lenses with different throw ranges to use in specific or specialized situations. This provides the user with far more flexibility than a fixed lens. The same projector can be placed in the front of the room close to the screen using an ultra-short throw lens or way in the back of a large lecture hall using a long throw lens.
Interchangeable Epson Pro Lenses