Page 2.14
105-453B January 2007
2. Installation
Digital Projection
LIGHTNING 35HD-T, 40HD-T
User Manual
Notes
The Throw ratio for a particular
lens is
fi
xed, but assumes that
the image
fi
lls the width of the
DMD.
For images that do not
fi
ll the
width of the DMD, the Throw
ratio is effectively increased.
To correct for this in these
calculations, a Throw Ratio
Factor (TRF) is used.
Lens extension is measured
when the lens is focussed at
in
fi
nity, and fully extended.
At other focus settings, the
extension could be up to 10mm
less
Useful lens calculations
The following lens calculations may be useful:
Throw ratio
= Throw distance
Screen
width
Throw ratio factor (TRF)
=
DMD width in pixels
= 2048
image width in pixels
image width in pixels
Therefore:
Screen width
= Throw distance (from outer end of lens)
Throw ratio x TRF
Throw distance
= Screen width x Throw ratio x TRF
The throw distance calculated above is to the outer end of the lens. For each lens,
the nominal distance between the front of the projector and the outer end of the lens
(lens extension) will be as listed below:
lens extension
1.0: 1
fi
xed lens
103-350
185mm
(7.3in)
1.25 - 1.45: 1 zoom lens
103-351
161mm (6.3in)
1.45 - 1.8: 1 zoom lens
102-451
109mm
(4.3in)
1.8 - 2.4: 1 zoom lens
102-676
97mm
(3.8in)
2.2 - 3.0: 1 zoom lens
102-677
53mm
(2.1in)
3.0 - 4.3: 1 zoom lens
102-678
98mm
(3.9in)
4.3 - 6.0: 1 zoom lens
104-189
170mm
(6.7in)
lens extension,
measured from front
of corner post
