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Positioning your projector 13
signal) will display in a 4:3 aspect ratio (and will require an additional 33% display height
than that of the scaled 16:9 aspect image projection area).
IMPORTANT: Do not select a permanent projector position based upon a 16:9 projection if you
will ever need to select an input other than composite Video being fed a 16:9 aspect signal.
The projector should always be placed horizontally level (like flat on a table), and positioned
directly perpendicular (90° right-angle square) to the horizontal centre of the screen. This
prevents image distortion caused by angled projections (or projecting onto angled surfaces).
The modern digital projector does not project directly forward (like older style reel-to-reel
film projectors did). Instead, digital projectors are designed to project at a slightly upward
angle above the horizontal plane of the projector. This is so that they can be readily placed
on a table and will project forward and upwards onto a screen positioned so that the bottom
edge of the screen is above the level of the table (and everyone in the room can see the
screen).
You can see from the diagram on page 15, that this type of projection causes the bottom edge
of the projected image to be vertically offset from the horizontal plane of the projector. If the
projector is positioned further away from the screen, the projected image size increases, and
the vertical offset also increases proportionately.
When determining the position of the screen and projector, you will need to account for
both the projected image size and the vertical offset dimension, which are directly
proportional to the projection distance.
BenQ has provided a table of 4:3-aspect-ratio screen sizes (see "Screen size chart" on page
15) to assist you in determining the ideal location for your projector. There are two
dimensions to consider, the perpendicular horizontal distance from the centre of the screen
(projection distance), and the vertical offset height of the projector from the horizontal edge
of the screen (offset).
How to determine the position of the projector for a given
screen size
1. Select your screen size.
2. Refer to the table on page 15 and find the closest match to your screen size in the left
columns labelled '4:3 Screen Diagonal' and '4:3 Aspect in mm'. Using this value, look
across this row to the right to find the corresponding average distance from screen
value in the column labelled 'Average'. This is the projection distance.
3. On that same row, look across to the right column and make note of the vertical Offset
value. This will determine the final vertical offset placement of the projector in
relation to the edge of the screen.
4. The recommended position for the projector is aligned perpendicular to the
horizontal centre of the screen, at the distance from the screen determined in step 2
above, and offset by the value determined in step 3 above.
For example, if you are using a 120-inch screen, the average projection distance is 4757 mm
and with a vertical offset of 229 mm.
If you place the projector in a different position (to that recommended), you will have to tilt
it down or up to center the image on the screen. In these situations, some image distortion
will occur. Use the Keystone function to correct the distortion. See "Correcting keystone" on
page 24 for keystone correction.