Full lens calculation example
Your screen is 4.5 m wide; you wish to place the projector
approximately 11 m from the screen. You use a WUXGA
projector; the source is 4:3.
1. Calculate TRC as follows:
1.6
1.33
TRC =
= 1.2
2. Calculate the throw ratio:
11
4.5 x 1.2
Throw ratio =
= 2.04
3. Find a match in the lens table.
The table shows that the lenses matching a throw ratio
of 2.44 are:
• the 1.87 - 2.56 : 1 zoom lens
• the 1.50 - 2.17 : 1 zoom lens
• the 1.72 - 2.71 : 1 zoom lens
4. Check whether the lens covers the required throw
distance.
The range quoted for the 1.87 - 2.56 : 1 zoom lens is
4 m - 24 m. The required distance of 11 m is within the
range.
The other two lenses have a range of 5 m - 25 m, also
within the range.
Notes
You can also use the information
in Appendix B: Lens Charts to
choose a lens.
For information about individual lens
part numbers, see Appendix A:
Lens Part Numbers at the end of
this document.
INFORMATION YOU NEED FOR THESE CALCULATIONS
• The TRC formula
• The TRC table (to use instead of the formula)
Image format WUXGA projector
2.35:1 (Scope) TRC not used
1.85:1 (Flat) TRC not used
1.78:1 (16:9) TRC not used
1.66:1 (Vista) TRC not used
1.6:1 (16:10) TRC not used (native resolution)
1.33:1 (4:3) TRC = 1.2
1.25:1 (5:4) TRC = 1.28
• The throw ratio formula
• The lens table:
Throw ratios for 1080p and WUXGA Throw distance range
0.67 : 1 xed lens 1.1 m - 10 m (3.6 ft - 32.8 ft)
1.12 : 1 xed lens (3 m - 15 m) 3 m - 15 m (9.8 ft - 49.2 ft)
1.12 : 1 xed lens (1.2 m - 2 m) 1.2 m - 2 m (3.9 ft - 6.6 ft)
1.16 - 1.49 : 1 zoom lens 3 m - 15 m (9.8 ft - 49.2 ft)
1.39 - 1.87 : 1 zoom lens 4 m - 24 m (13.1 ft - 78.7 ft)
1.87 - 2.56 : 1 zoom lens 4 m - 24 m (13.1 ft - 78.7 ft)
2.56 - 4.17 : 1 zoom lens 9.1 m - 45 m (29.9 ft - 147.6 ft)
4.17 - 6.95 : 1 zoom lens 12 m - 80 m (39.4 ft - 262.5 ft)
6.93 - 10.34 : 1 zoom lens 12 m - 80 m (39.4 ft - 262.5 ft)
1.50 - 2.17 : 1 zoom lens 5 m - 25 m (16.4 ft - 82 ft)
1.72 - 2.71 : 1 zoom lens 5 m - 25 m (16.4 ft - 82 ft)
2.15 - 3.36 : 1 zoom lens 5 m - 25 m (16.4 ft - 82 ft)
DMD™ aspect ratio
Source aspect ratio
TRC =
Throw distance
Screen width x TRC
Throw ratio =