projector based on the type of optical
train you can get
really important parameters:
Lens throw ratio (D/W)
= distance with screen / width of image
<1.5 short Throw Ratio, use 50mm optical train
>1.5 use Heligon optical train
1920x1080 (FullHD) otherwise
1024x768 (XGA). Be careful, a number of advertisements are misleading.
This is not because the projector accepts the HD format that it really
projects at this resolution.
minimum. Beware of advertising
announcing 1:50000 or 1:10000
more and more projectors use
an automatic iris. When projecting stars, the iris is useless! and the
contrast falls to 1:2000 or less!
projectors are never able to
produce an intense black. There are still large differences depending
models. This setting isn't always well documented and it is a pity.
of the time, the more the projector is capable of sending level of
the more blacks looks gray.
choosing a 5000 lumens
beamer on a dome of 5m is useless, because it comes at a good level of
illumination with 1000 lumens. All we can get with a big black
is so much slimy gray, instead of a deep black with a less energetic
choice of techniques
or LCD (LCoS is more expensive)
by far the DLP, because even
with a FullHD LCD, the screen effect is clearly visible, which is
despicable on a dome ...
new LED/Laser technology seems
very promising and is very attractive in terms of lamp lifespan.
But not perfect at the moment.
50 mm optical train
P1623 (1200p - better choice with 50mm optical train)
Basic bloc page for more choice
5280U 1920x1200 (4200 EUR)
offers improved brightness, contrast and some options as substantial
alignment. Anyway, there is trouble in the dark area of values needing
some adjustments with the milkyway.
DESIGN F22 1920x1200 (8
000 EUR) perfect.
F50 2560x1600 is far better
but very expensive (15 000 EUR).
choice of the projector between
1000 and 2500 lumens seems appropriate in all situations, until at
6 m in diameter. With 6 to 8 m, 3000 to 5000 lumens is a better choice.
Yves LHOUMEAU &