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CE Pro Magazine,
November 2002
5 Tips to Help Optimize a CRT Installation
By Gary Guidi, President
Crystal View, Inc.
THROW DISTANCE: Your customers may say that
they intend to use their home theater to
view wide-screen DVDs and HDTV only. However
the reality is that for some time to come,
they will want to watch pre-recorded or
broadcast letterboxed movies. Letterboxed
movies are formatted to be viewed at full
width on a 4:3 screen with visible black
bars above and below the image. Therefore,
when you install a system with a 16:9 or
other wide-format screen, you must be able
to expand the size of a 4:3 image, that
normally has black bars on the sides, to
fill the width of the screen. Otherwise, you
will end up with a small picture in the
center of the screen with black bars on all
four sides. In order to be able to “blow up”
the letterboxed picture to full width, you
will need to place the projector up to 25
percent further from the screen than the
published throw distance formula indicates.
Note that there are a few high-end scalers
that have the special capability of
expanding a letterboxed image electronically
to save you from having to deal with this
issue.
SCREEN SIZE and PRIMARY VIEWING DISTANCE: A
person with perfect 20:20 vision will just
be able to discern the smallest details of a
perfectly projected 1080i HDTV image, when
viewed from a distance of 1.87 screen
widths. At that critical distance, the
picture will fill about a 30-degree angle of
view. It will not only look large, but
action at the edges of the picture will be
within their peripheral vision and provide a
strong sense of motion. At or beyond that
distance, the image will be very sharp,
creating the impression of being there live
and “looking out of a window”.
Since even the best DVD provides only about
a third of the detail of HDTV, to get the
same resolution clarity, they would have to
be three times further away from the screen
-- regardless of how the picture is
“scaled-up”. Since they won’t move further
away from the screen than that, any other
standard NTSC picture will look softer and
less real than HDTV. Accordingly, in most
home theaters, an 80 to 96 inch wide screen
is ideal for maximum picture quality and a
low-gain surface, which illuminates evenly,
will be sufficiently bright with a CRT
projector.
BLUE FOCUS: Our eyes have far fewer blue
receptors than red and green, so you really
can’t see when the blue is perfectly focused
when you are at the back of the theater
adjusting the projector. To properly do
this, place an assistant at the screen, and
have him trot back and forth while adjusting
the blue focus for minimum perceived
brightness. That works because an unfocused
dot or line excites more receptors in your
eye and thus appears to be brighter.
COLOR TEMPERATURE: From all the reviews I
have read, it seems rare for a video display
of any kind to be shipped with an accurate
6500-degree color temperature. However, no
two kinds of white surface reflect exactly
the same color balance. The final
calibration setting should be made on the
customer’s screen unless you know it is the
same screen material used at the factory.
The readings must be taken in an absolutely
dark room. And, the color of the room will
be reflected back onto the screen by light
from the screen. This makes a good argument
for dark, neutral walls.
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Gary Guidi is the co-founder of
Massachusetts-based HI-REZ Projections, Inc.
The company is one of the world’s largest
video projector service centers. Gary can be
reached at gguidi@crystalviewinc.com
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