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9
2.General
Rear projection
The projector is installed, either in a table mount or ceiling mount configuration, at the other side of the screen opposite the
audience.
AUDIENCE
BACKSTAGE
R/C
R/T
FLOOR
SCREEN
Rear projection
Positioning the projector
FLOOR
SCREEN
SCREEN
PD
A
CD
SCREEN
SW
SW
SH
B
SH
B
CD
Positioning projector
The projector should be installed at right angles (horizontally and vertically) to the screen at a distance PD. Note the distance
(A) between lens centre and table surface is slightly variable. This distance (A) is nominal 8.3 cm in case all feet are turned in
completely and the vertical lens shift is set to zero (0).
On axis / off axis projection
The position of the projector with reference to the screen may also be different depending on the installation. Basically the
projector can be positioned in On-Axis or Off-Axis configuration. On-Axis configuration means that the projector is positioned
so as to have the centre of the lens coinciding with the centre of the screen. Off-Axis projection is obtained by shifting the
lens up, down, left or right. Several parameters can be calculated determining the position in any installation.
Formula to calculate the distance CD for On-Axis projection: CD = SH/2 + B - A
Shift range
The lens can be shifted with respect to the DMD (P) which result in a shifted image on the screen (Off-Axis). A 100% shift
means that the centre point of the projected image is shifted by half the screen size. In other words, the centre point of