question about tolerances


May 21, 2020
Real Name
Hi, I'm hoping to get some perspective on tolerances here.

I'm looking at setting up a projector in my living room, an Epson 3800 (chosen for a variety of reasons, including budget and the need for both vertical and horizontal lens shift because of a window) and a 120" screen.

My distance from rear wall to screen is 13' exactly. The 3800 is 13" deep. According to Epson's throw calculator, I need a minimum of 11' 7.3." Thirteen feet minus 13 inches (the projector's depth) gives me 4.7" of wiggle room. Assuming 2 or 3" behind my projector for cables, I'm looking at a total distance between screen and lens of 11' 8" or 11'9".

I'm cutting it close, within an inch or two. Can I trust the calculators to that degree? Will lens shift (not keystone) have any impact? I would hate to step down to a 110" screen. I'm also not in a position for various reasons to mount an ultra short throw and would prefer to stick with the 3800.

Thanks in advance for any wisdom.


Second Unit
Jan 24, 2010
East Tennessee
Real Name
I've found the figures in the manual are not exact. The best ways are either to pick a screen size under the maximum and use the zoom to shrink the image to fit, or get the projector, try it out and then select screen size. I made my screen from fabric and sized the frame I stretched it on to the size I wanted. I also found the image size slightly different from the size predicted in the manual. I anticipated not having the throw distance required for the screen size I wanted when building my house. I had plumbing and wiring routed to leave the center of the wall clear, and reinforced the area of the soffit holding ventilation in the adjacent room to allow mounting a projector, if necessary. When I tried my projector, I found the image was smaller than I wanted, so I took a saw to the wall and made a hole to project through. I made a frame to hold optical grade glass perpendicular to the beam from the outside, and beveled the dry wall on the theater side.

It looked good when everything was complete. If you go that route, I might add a cautionary note. Your significant other may not share your vision. I found it went over better explaining what I had in mind after making the hole in the wall. After their initial surprise and expression of astonishment, they get over it, after awhile anyway.

By the way, check to see how much room you may need to allow ventilation. If the vents are in the back, they usually require a few inches from any wall or obstruction to allow adequate flow. Lens shift is also limited at the maximum amounts, that is, at extremes in one direction, less perpendicular shift is possible. I'm not sure if image size is effected, but any effect would be minor. You can probably download the manual online from the manufactures website before buying the projector and find the information there.
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