The "brightness" figure for a projector is given in lumens, but that's a
measure of the light energy leaving the lens; it's one factor in determining
the perceived brightness of the image, the others being the screen size, the
screen "gain," and the ambient light level in the viewing room. Without
knowing those, the only advice someone could give you would be to get the
projector with the biggest output spec in lumens that you could afford, but
there's a significant chance that you'd wind up buying excessive brightness
at the expense of other features.
Not much choice here, really. You're going to want 1920 x 1080 pixels, and
that's pretty much all you'd find anyway. Lower resolution projectors won't
do Blu-ray discs justice, at least not on a larger screen.
Absolutely. First - how far will the projector be located from the screen?
You need to make sure the optics of the projector (the projection lens
system) are capable of producing the desired image size at that distance.
Also, unless the projector can be mounted such that it is facing the screen
"squarely" (i.e., a line from the projector lens to the screen is
perpendicular to both), you will wind up with a distorted image (look up
"keystone distortion" for an example). Some projectors can correct for this,
if such correction is needed.
You should also look into the basic imaging technology used by the projector.
Lots of projectors today use Texas Instrument's "Digital Light Processing"
(DLP) technology, in which the image is formed on a chip carrying literally a
couple of million tiny little square mirrors. But this technology doesn't
inherently provide a color image, so to get full color images you either need
to show the red, green, and blue images on a single chip in rapid succession
(called "field-sequential color") or use three of these imaging chips, one
for each color. The three-chip types are obviously going to be more
expensive, but provide the best image and avoid a problem that's inherent in
the single-chip designs known as "color breakup" or the "rainbow effect."
Some people are very sensitive to this effect, in which you will perceive
colored fringes around moving objects within the image, or if you move your
head rapidly such that the image moves across your field of vision. If
you're not overly sensitive to the problem (I'm not, personally), single-chip
projectors will be fine choices; if you are, you may need to look for a
three-chip design or use some other imaging technology. LCDs are the other
major imaging device common found in consumer projection. They typically
don't provide the high contrast of the DLP imagers, and have an overall
different "look" to the image. Shop and compare.)
Finally, you'll need to consider other features that may be of concern to
you. Top of that list is likely what inputs you need: HDMI is the de-facto
standard digital interface for HDTV today, but you may also need the
projector to be able to handle the older analog TV connections standards
(composite or component video, typically using "RCA" jacks, or "S-Video"
which is typically on a DIN connector) or to accept video from personal
computers (which may provide HDMI, but which might also use VGA, DVI, or
DisplayPort outputs; of those, only DVI is directly compatible with HDMI).
Bob M.
