Originally Posted by BRI59
So the lamp on lower lumens projectors may dim to a disappointing level within a couple of hundred hours. This effectively means that a demo of a huge number of projectors is a waste of time, because after very moderate use they will not be showing a good enough picture, and you will wish you had not made the purchase. This is very concerning!
What I've been doing is calculating the screen light output (wrote a small excel spreadsheet to do so) based on screen gain, lumens, and diagonal screen size. The following is also a good calculator that automatically adds in aging of the bulb:http://www.scottgammans.net/scooterp...calculator.xls
(Written by Scott Gammans) Scott's progam uses width of the screen, which I find confusing, so I made my own Excel program that uses diagonal size of the screen (my program also uses inverse tangent, which I personally found easier to understand). If you get 12ftL of light output with a new bulb at the calibrated low level output, that's very good. That means you can lose 25% and still have a relatively bright output from the screen. If you get less than 12 using your screen size, screen gain, and the projector's lumen output, you're in trouble.
For instance, the Mitsubishi HC5000 1080p projector supposedly only produces about 400 lumens in HIGH (not low) light output mode. As I plan on using a 0.9 gain screen, if I wanted to choose this projector, I'd have to use a much smaller screen size. Either that or not use an acoustically transparent screen and I would have to choose a higher gain screen.
This is what makes choosing a projector and screen so hard: you have to choose both the screen and the projector to get enough light output over the life of the bulb; you have to determine whether you want a dungeon or the ability to have some lights on; you have to wade through a myriad of reviews where some people hate the exact same projector (or screen) that others love; and you have to meet your monetary requirements. And usually, you never get to see the projector and screen you want to buy in action, properly calibrated, and in a room that's similar to yours. It's not an easy process.