Cybertea,

Thank you for using the Dell Community Forum.
There are no measurement specifications for how far/close a projector is to a display surface, so I don't have
an exact measurement for you. The closer you move a projector to a surface the smaller the image will be.
The farther you move a projector to a surface the larger an image will be.
The projector has a 1.2x manual zoom lens which can be adjusted by using the "zoom tab" on the top of the projector.
Projector Features.
Projector Users guide .
You may also want to switch the video mode to the movie setting, if you are going to be watching movies.
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Video Mode
The Dell 2200MP Microprojector has preset configurations that are optimized for displaying data (PC Graphics) or video (movies, games, etc.). Press Video Mode button to toggle between PC mode, Movie mode, sRGB, or User mode (for user to setup and save preferred settings). Pressing the Video Mode button once will show the current display mode. Pressing the Video Mode button again will switch between modes.
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Here is a nice tool to find approximate sizes based on projectors.

http://www.projectorcentral.com/projection-calculator.cfm