jakdedert wrote:
Arfa Daily wrote:
Not really a repair thing - just a comment on product uselessness
really. My next door neighbour treated himself to a bunch of home
cinema gear this Christmas, including a Panasonic DVD player, a
Panasonic DVD / HDD recorder, a Yamaha digital sound projector, (
whose performance is unbelievably good ) and the crowning glory,
Panasonic's latest all singing and dancing front projector with enough
output to work in virtual daylight. All OK so far. He came round to
see me the day after Christmas, bearing bottles of beer - so that was
OK - and wanted me to go round so that he could show me his home
cinema that he had built. As we were walking back round, he told me
that the only problem that he had, was a keystone-distorted picture in
the horizontal. No problem, I told him. There will be menu settings
for N-S and E-W keystone correction. No, he said, there's only one. I
told him that he must be mistaken, as they would not just put one
correction in, as it's so easy for them to distort the image within
the projector, to compensate for optical misalignment.

However, he was right. There is electronic compensation for up-down
tilt of the projector - and the range is huge. You could literally
stand the projector on the floor pointing up at the wall by 30
degrees, or likewise, down by the same amount from the ceiling, but
there is no way to correct for the one foot !! horizontal misalignment
that he was forced to have because of the only places that the screen
and projector shelf could go. Suspension from the ceiling to place the
projector exactly in front of the screen was not an option. There is a
mechanical lever on the front, which shuffles the lens about, and
moves the image around, but this in no way allows you to compensate
for the trapezium shaped picture that is a result of this
comparitively small misalignment. Just how crap is that ?? Considering
that this unit is designed for use in the home, where alignment
conditions are very likely to be less than optimum, just what were the
designers thinking of, when they left this important geometry
adjustment out ? Perhaps I'm missing something, but I don't think so.
Both myself and my neighbour spent a long time reading the book of
words, and could find no references to any correction that could be
made in respect of this type of image distortion. If anybody can
enlighten me as to anything different, I'd be really glad to hear what
you have to say ...

Arfa


(In an LCD projector, there is no magnetic N-S correction.) Granted,
trapezoidal distortion is annoying, but it's ridiculously easy to
compensate for. If the projector is already fixed into position and
can't be moved, a relatively minor correction in the *angle* of the
screen will do it. Simply move the side of the screen where the image
is larger slightly closer to the projector. Usually an inch or two will
do it.

This was an error in installation, which even a novice installer should
have corrected for. The keystone correction is only for convenience.
It's rare for there to be an instance where it's acceptable to place the
projector vertically level with the center of the screen, without
affecting sight lines. That's why there's some method of keystone
correction in nearly every projector. Getting it in the middle
*horizontally* should be a given...and trivial to achieve.

Electronic geometry corrections affect the resolution available anyway,
as pixels are sacrificed for geometry. Optical or mechanical (moving
the screen or optics) solutions offer the highest degree of accuracy,
resolution and viewability.

Given that he's spent so much on gear, it would make sense to install it
all correctly. If he had it done, he needs to get the installers out to
correct it. If he did it himself....

jak

Okay...rereading the OP, I see where he was forced to put the projector
off-center. In that case, changing the angle of the screen is required.
Some forethought in the installation might have produced a projector
which would have filled the screen from a closer distance--possibly
allowing center placement--but he's locked in now. Angle one side of
the screen (the one with the large side of the trapezoid) toward the
projector. Depending on the degree of distortion, the distance from
screen to projector, the size of the image desired and the screen
mounting method, it might yet be a trivial fix...but it must be done to
obtain a 'square' image.

This is an instance in which professional consultation might have saved
money. I've seen few projectors with trapezoid correction.

jak