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Catching on to the cathode ray:
We cover the CRT, or cathode ray tube, in the first section of this chapter, so
we’re not going to get into a long discussion about what they are or how they
work here. However, that good, old-fashioned tube is not only the heart of
most conventional TVs, but also the centerpiece of the most sophisticated,
highest-quality projector systems (which is to say, the most sophisticated,
highest-quality displays, period).
CRT projectors, particularly front-projection systems, can provide the highest
resolution (including full HDTV support), the most excellent color, and
a bright picture with a superb contrast ratio. (If any of these terms seems
unfamiliar to you, refer to Chapter 13.) CRT projectors also provide the best
reproduction of black tints — significantly better than any of the other projector
types available.
Unlike direct-view CRT displays, which use a single picture tube, CRT projectors
use three separate tubes — one each for red, green, and blue. The extra
tubes make the setup and calibration more complex because the light projection
from these three CRTs must be converged (aligned so that they each hit
the screen at the same place). If you’ve seen bad projection TV before, with
inaccurate color reproduction and colored “halos” around objects, you’ve
probably seen a system that has not been properly converged. It’s not pretty.
Convergence on projection systems tends to drift over time, so you need to
think about resetting the convergence a couple of times a year. Luckily, many
RPTVs now include an automatic convergence system that simplifies this
process. In Chapter 19, we discuss how you can do your own calibration or
hire a professional to calibrate your projection system.
Perhaps the biggest factor to consider when comparing CRT projectors is
tube size. In the RPTV realm, this isn’t a huge deal. Almost all RPTVs have
the same size (7-inch) tubes, but front projectors have tubes in the 7-, 8-, and
9-inch ranges. Bigger tubes bring with them sharper, more detailed pictures,
but at a considerably higher price. In fact, the price differential between a
7- or 8-inch projector and a 9-inch model can be striking. You can get a decent
7-inch front projector for under $10,000 (still a lot), but 9-inch CRT projectors
usually start off in the $30,000 range.
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