My projector to the screen? Probably 14-15 feet or so. The room is 19' long and the projector is about 3 feet from the back wall, and the screen is about a foot away from the front wall.
The back row viewpoints are about 17' view distance from the screen and the front seats (which are the seats everything was optimized around) are 9 or 10' away from it. The projector is mounted between the front and back rows, but it's closer to the back than the front row.
FWIW my "beta theater" build (and interest in creating my own theater) started off when the in-laws added on to their house in 2012. They had a "media center" built into their great room with a large cavity between shelves for a TV to be mounted inside. I got the idea when I salvaged an old SVGA 1000 lumen projector from a scrap pile at one of my clients and hung a sheet over the TV. That morphed into them buying a pull-down vinyl projector screen (which blended in/was concealed nicely by the molding at the ceiling) and eventually a 1080p projector. IIRC it was an Epson Home Cinema 8350. Respectable and not bank breaking.
You WILL notice a difference on a large screen between SD and FHD. Past FHD, it's more subtle... but still profound IMO.
I bought my 5040UB in spring of 2019, nearly a year before I finished the basement and theater project. I got it on sale for about $1200 (normally $3k) as Epson was selling of their RMA'd and refurbished stock just before they announced the 5050UB.
I'll post what pics I can find; I think have a comparison of the 8350 against the 5040UB I have currently, along with some memory lane photos that document the humble origins of my journey thus far.
.......
I sure do. These two comparisons are taken with the same exposure of the UHD/4k version of the film. The first image was with my 5040UB, the second was with the 8350 I had the in-laws buy for their room. The most obvious difference is the brightness; if you zoom in you can see a little more detail on the 5040, but not quite 4k detail.
If I go back further, I have the "discount screen" and free SVGA projector combo I hung at the in-laws which was the v1.0 concept for what I ended building for myself.
It sure made the TV look downright puny!
And at last, the genesis of the idea... a drop cloth and painter's tape. Let's call it v0.1.
I don't know why, I just suddenly felt like revisiting all the iterations of projectors and screens I've futzed with.