Specifications

Appendix C Display Issues 249
OPTICAL LINEARITY When using multiple overlapping projectors, optical linearity is important.
Deficiencies in optics often show up as barrel or pin-cushion distortion. This
may be particularly troublesome when using short-throw, wide angle lenses
(often desirable for rear-projection).
The best way to avoid this problem is to choose projectors with high-grade
optics, and to ensure that your optics are properly matched for the desired
projection distance.
◆ HINT: If you’re using zoom lenses, you may be able to obtain better linearity
by changing the focal length and moving the projector accordingly.
Correcting Optical Errors If necessary, use the geometry correction feature built into WATCHOUT
(page 160) to compensate for the distortion. Some projectors have similar
capabilities built in.
STEREOSCOPIC PROJECTION Stereoscopic (“3D”) projection uses twice as many projectors as regular
presentations. Projectors are fitted with filters matching the filters used in the
glasses worn by the viewers. Special care must be taken when choosing the
screen material – particularly when using polarized filters. It may be hard to
find a screen material that works well for polarized stereoscopic projection,
while still avoiding hot-spots (see previous page).
An alternative to polarized filters is the Infitec color filters, as this technology is
more accommodating in terms of screen material.
http://www.infitec.de/
Pin-cushion and barrel distortion.