Specifications

246 Appendix C Display Issues
from most professional screen manufacturers (for example, “Aeroview 100”
from Stewart Filmscreen Corporation; http://www.stewartfilm.com/).
Edge Blend Areas Banding and other artefacts may appear in the overlap areas of edge-blended
images. There are essentially three kinds of problems:
Too Dark, Bright or Uneven Overlap. It may be difficult to obtain a
perfectly invisible edge blend for all image types. You may have to locate a
typical or particularly problematic image in your presentation and tweak the
edge blend curve using that image for the best possible result (see “Edge
Blend” on page 121).
Non-linear Gamma Settings. Most LCD and DLP projectors have a
gamma curve setting, often with a number of standard curves to choose from.
In order to achieve maximum perceived brightness, such projectors often come
preset to some high brightness gamma curve. While such a gamma curve may
provide some additional brightness, its non-linear nature tends to interfere with
the ability to achieve a smooth edge blend. Furthermore, it also results in
washed-out colors and a general lack of contrast. To avoid this problem, chose
a more linear gamma curve, often called “Photographic” or “Video”.
Projecting a grayscale gradient, or a set of gray bars (as seen in the test image
on page 165) often reveals problems associated with a non-linear gamma.
Attempt to find a setting that shows a linear gradient, or a clear distinction
between each gray bar.
Gray Boxes in Dark Images. Due to the poor contrast ratio of some
LCD and DLP based projectors, lighter areas in the overlaps of black, or very
dark images are sometimes inevitable. You can minimize the effect by
reducing the light output of the projectors (for instance, by switching to a “low
brightness” or “economy” mode), or by increasing the ambient lighting in the