Image brightness (1 Viewer)

Question;

What is the image brightness in a commercial Imax theater. And if I want to duplicate this level in a home theater, how do I calculate the lumen level needed from the projector for a given screen size and type?


I am in the preliminary design stage but screen size will be either 110 or 120 inches. and I want to be both 3d and 4k capable. Primarily for two people. When I visit a commercial theater, I usually sit in the row just above the middle cross aisle as I like the screen to fill most of my vision. (How someone could ever watch a movie on a tablet or smartphone is a total mystery to me)

After prowling around on web search results, the only mention of screen brightness I found for IMAX was from a forum post- 11 foot Lamberts. The IMAX site doesn't give much on specifications. The SMPTE recommendation for commercial cinemas is 12 to 16 fL.


The theoretical formula for calculating screen brightness in a preliminary design is: claimed projector lumens divided by screen square footage x screen gain = foot Lamberts. However, it's not that simple, since claimed projector maximum lumens is not a reliable metric, due to many factors. Also, claimed screen gain spec from manufacturers is also not a reliable metric. Varying distance from the screen to the projector lens can also affect screen brightness. If you are planning a CinemaScope aspect ratio screen, additional factors can affect final achieved screen brightness.


The solution, short of setting up and measuring actual screen brightness? Over-build the system. Projector lamps dim with age (even LED lamped models), most significantly within the first few hundred hours for non-LED lamped models. So, start with an extra bright theoretical calculated performance level of 20 fL or better.


Best regards and beautiful pictures,

G. Alan Brown, President

CinemaQuest, Inc.

A Lion AV Consultants affiliate


"Advancing the art and science of electronic imaging"