Just for fun, I've been playing with some numbers.
- Sitting 13 feet from a 166 inch screen (144x82 inches) means you have a 50 Degree FOV.
This means you're within the THX recommended 8.6 to 18.6 feet ( 70 - 35 degrees FOV respectively )
- Projecting on the wall, I gave you a screen reflectivity of 1.0 - On High (1600 lumens) screen illumination is almost 20 foot-lamberts.
Professional theater projectionists claim this illumination is at the top of ideal, but for a dark room.
I on the other hand, could definitely benefit from more size, but because I'm smaller (LOL) I can run the lamp in economy mode and still have good brightness.
- A single row of seating is 9 feet from a 96 inch screen (84x47 inches) which is a 42 Degree FOV.
I too am within the recommended THX FOVs, but would rather be on the higher side than where I am.
- Projecting on my HCG screen (I used 0.8 for reflectivity) - On Low (~1000 Lumens) illumination is over 29 foot-lamberts.
This is actually too bright according to most professionals. It causes retinal retention, confusion and eye strain in a dark room. However that's probably why I like it when I have some room light on, which is at least half of my viewing.
Just thought it might help others to appreciate the numbers and to get a sense of what they might be able to do with their setups.
Incidentally, I have the original 1080 (1200 lumen) projector, not the 1080UB (1600 lumen) unit most of you have. This is taken into account in the numbers above. (Credit to my calculator and then to carltonbale.com's Excel spreadsheet - when I realized there was an easier way!)