How far back does the projector go?
Throw distance range and the brightness the screen size calls for.
- Image size
- 104.6″ wide, 58.8″ tall
- Lens to screen
- 10 ft 6 in to 16 ft 7 in
- Brightness to look for
- 2,000 lumens or more
Mount the lens anywhere in the green strip and zoom to fit. Leave a foot of slack at each end so you are not at the limit of the zoom.
How this is worked out
Throw distance is the lens throw ratio times the image width. A zoom lens gives a range, so you get a nearest and farthest mounting position.
Brightness is screen area in square feet times a target in foot-lamberts, divided by screen gain. Rooms with the lights on need a much higher target than dark rooms.
Common questions
How do I calculate projector throw distance?
Multiply the lens throw ratio by the width of the image. A 120-inch 16:9 screen is about 104.6 inches wide, so a lens with a 1.5 throw ratio sits about 157 inches, or 13 feet 1 inch, from the screen.
How many lumens do I need?
Multiply the screen area in square feet by a brightness target, then divide by the screen gain. Use 16 for a dark room, 40 for dimmed lights and 60 with the lights on. A 120-inch screen is about 43 square feet, so it needs roughly 1,700 lumens with dimmed lights and 2,600 with the lights on. Buy some headroom, because light sources dim with age.
What is a short throw projector?
A short throw projector has a throw ratio below about 1.0, so it sits closer to the screen than the image is wide. Ultra short throw models, below about 0.4, mount just above or below the screen and avoid shadows from a presenter.