3M
Overhead Projector 9800 Series
Section 1 – Introduction
1-6
9800 Service Manual
3M 1996
1-2-5. Calculating Projector-to-Screen
Distance For Desired Image Size
The size of the projected image is determined by the
following factors:
•
Projector-to-Screen Distance
•
Focal Length of Projection Head
•
Stage/LCD Panel Aperture Size
•
Screen Size (Image Size)
For a given screen size, use the following formula or
refer to Figure 1-6 to calculate the projector to screen
distance needed to fill the screen.
D = F ( S + 1)
A
D =
PROJECTOR-TO-SCREEN DISTANCE
F =
FOCAL LENGTH OF HEAD
S =
SCREEN SIZE
A =
STAGE/LCD PANEL APERTURE SIZE
For example: To fill a 152 cm x152 cm (60 in. x 60
in.) screen, how far from the screen should you
position a 285 mm (11.2 in.) stage projector with an
342 mm (13.5 in.) focal length.
D = 34.2 cm ( 152 cm + 1)
28.5 cm
D = 217 cm (86 in.)
To use Figure 1-6, locate the specific screen size on
the right and read the corresponding projector distance
at the bottom. For LCD panels, locate the LCD panel
size in the chart and read the corresponding projector
to screen throw distance to the right.
Note
Focusing an overhead projector at extreme
distances (near or far) may result in poor
overall image quality and require a Color
Tuning adjustment. See 1-2-4.
