Projector brightness is often compared as a single lumen figure. In a cinema, that number only becomes useful once it is placed inside the complete projection system.
Image area changes everything
The same projector has to spread its light over a much larger area as screen width increases. A projector that is generous on one screen may be operating near its limits on another.
Screen material changes delivered light
Gain, weave or perforation, viewing angle and material choice all influence how much light reaches the audience and how evenly it is distributed.
HDR creates headroom demands
Projection cannot reproduce HDR in the same way as a small emissive display, so tone mapping and available peak brightness have to work together. More headroom can provide greater flexibility, but it still needs correct calibration.
Specify to the room
We therefore treat brightness as a calculated system requirement tied to image width, screen material, throw, lens choice, room conditions and intended operating mode.