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Full lens calculation example
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 1.2 = 2.04
3. Allow a tolerance of +/- 3% in the throw ratio calculation and
find a match in the lens table.
The table shows that the matching lens is the 2.00 - 4.00:1
Zoom lens.
4. Check whether the lens covers the required throw distance.
The focus range quoted for the 2.00 - 4.00:1 Zoom lens is
1.82m - 41.8m. The required distance of 11 m is within the
range.
Reference Guide
CHOOSING A LENS
INFORMATION YOU NEED FOR THIS CALCULATION
The TRC formula
TRC = DMD
Aspect Ratio / Source Aspect Ratio
TH
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
Throw Ratio=Throw Distance/Screen Width * TRC
Allow a tolerance of +/- 3% in the throw ratio calculation.
The lens table:
Throw ratios
0.38:1 fixed
0.9 - 1.2 : 1 zoom
1.20 - 1.56 : 1 zoom
1.50 - 2.00 : 1 zoom
2.00 - 4.00 : 1 zoom
4.00 - 7.00 : 1 zoom
6.9 - 10.3 : 1 zoom
Digital Projection Ltd. M-Vision WUXGA Series
Focus Range
1.6m - 5m
0.92m - 10.6m
0.95m - 17.47m
1.24m - 16.4m
1.82m - 41.8m
4.38m - 74.5m
12m - 80m
Notes
Rev A January 2024
page 105
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