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Choosing a lens
Digital Projection Ltd. Titan Laser WUXGA
Full lens calculation example
INFORMATION YOU NEED FOR THESE CALCULATIONS
The TRC formula
The TRC table (to use instead of the formula)
2.35:1 (Scope)
TRC < 1, not used
1.85:1 (Flat)
TRC < 1, not used
1.78:1 (16:9)
TRC < 1, not used
1.6:1 (16:10)
TRC < 1, not used (native aspect ratio)
1.33:1 (4:3)
TRC = 1.2
1.25:1 (5:4)
TRC = 1.28
The throw ratio formula
Allow a tolerance of +/- 2% in the throw ratio calculation.
The lens table:
Throw ratios
Focus Range
0.67: 1 Super Wide fixed
1.1m - 10m
1.12 : 1 Wide Fixed
3m - 15m
1.16-1.49:1 Super Wide Zoom
3m - 15m
1.39 - 1.87:1 Wide Zoom
4m - 24m
1.87 - 2.56:1 Standard Zoom
4m - 24m
2.56 - 4.16:1 Semi Long Zoom 9.1m - 45m
4.16 - 6.96:1 Long Zoom1
12m - 80m
6.92 - 10.36:1 Long Zoom2
12m - 80m
Your screen is
4.5m
wide; you wish to place the projector approximately
11m
from the screen.
The source is
4:3
.
1. Calculate TRC as follows:
TRC = 1.6 / 1.33 = 1.2
2. Calculate the throw ratio:
Throw ratio = 11 / 4.5 x 1.33 =
1.84
3. Allow a tolerance of +/- 2% in the throw ratio calculation and find a match in the lens
table.
The table shows that the matching lens is
the 1.39 - 1.87 : 1 zoom lens
.
4. Check whether the lens covers the required throw distance.
The focus range quoted for the 2.2 - 3.67 : 1 zoom lens is
2.36m - 24.2m
. The required
distance of 11 m is within the range.
Reference Guide
Rev A January 2019
page 107
Notes