Rear Projection or high angles from the front?

In any case, pay special attention to the ambient and stray light hitting the

screen. The more light hitting the

screen, the more

power is going to be necessary to light it.

By the way, Backstage Handbook has a very useful chart on figuring out

projector sizing and ranges.

That in addition to this: (but I'm not sure where I got it from so that's a bad thing. Probably either Architectural Graphics Standards or Architect's Handbook of Formulas, Tables & Mathematical Calculations.)

Lenses and Focal points:

Screen Projection

The relationship between the positions of

the light source or the object (slide) and the

point where the transmitted rays from an

image is determined by the “

Lens Formula”,

When P= the distance from the object to the principal plane of the

lens,

Q= the distance from the principal plane to the

image, and

F= the

focal length of the

lens; than 1/P + 1/Q = 1/F.

The maximum distance between the first row of the audience and the

screen is determined by the maximum allowable angle between the sight

line from the first row to the top of the

screen and the perpendicular to the

screen at that

point. 30 to 35° is recommended.

The maximum distance between the

screen and the most distant viewer should not exceed eight times the height of the

screen image. A most distant viewer two to three times the

screen width is preferred.

Screen width is determined by the use of the appropriate

aspect ratio between the

screen image height and width.

Curvature of screens may reduce the amount of apparent

distortion for a larger audience area. Curvature of a larger screens may help to keep the whole of the

image in focus and may provide a more uniform distribution of

luminance.

Tilt all projection screens back half the angle of projection whenever the projection angle is over 15°.