HC4900 Projector - Light Leakage
When it comes to light leakage, the HC4900 does an excellent job, with virtually no light leakage, and what little there is, is a non-issue. The leakage comes out the lens, but is so dim, even compared to a "black" screen, that it's not worth considering.
Mitsubishi HC4900 Audible Noise Levels
This is easy. The HC4900 ties the HC5000 as the quietest home theater projector on the market. It claims an almost silent 19 db in low power, and even in full power, at 24 db, it is quieter than virtually all other home theater projectors, even when the others are in their "quiet modes". Outstanding!
HC4900 Projector Screen Recommendations
The HC4900, compared to the HC5000 is in the area of black levels, and corresponding shadow detail. For all but those trying to use an exceptionally large screen surface, I have to recommend HC gray projection screens, and for the first time in a while, I'll recommend some of the screens that were designed for older projectors with so-so black levels.
Even on my Firehawk, at 128" diagonal, I find the blacks coming out a bit to bright a gray for my taste. Remember, I'm spoiled, my JVC RS1 - at about twice the price of the HC4900, does the best job on black levels of any fixed pixel (LCD, DLP, LCOS) projector I have tested.
I would think Stewart's Grayhawk would be a great matchup, and for less money, alternates would include Da-Lite's HC Da-Mat, and Carada's affordable HC gray surface. Carada's is one I've never worked with, but from my understanding it is a dark gray, that should match very well. If you want to go larger screen sizes, the Firehawk, and Elite's HC gray surface, would be reasonable options. I'd avoid, in general, white surfaces, unless your primary purpose is non-movie content, such as sports viewing.