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Full lens calculation
Introducing TRC
The choice of lens will affect the image size and will address discrepancies
between the DMD™ resolution and the source.
When an image fills the height of the DMD™ but not the width, it uses less than
100% of the DMD™ surface. A lens chosen using the basic formula may produce
an image that is considerably smaller than the actual screen.
To compensate for loss of screen space in such situations, you need to increase
the throw ratio using a Throw Ratio Correction (TRC).
Example
Fig. 1 illustrates a 4:3 image within a 16:9 display.
When a 16:9 projector is used for a 4:3 image, the image does not fill the width of
the DMD™, creating a pillarboxing effect - blank spaces to the left and right.
Fig. 2 shows the same image projected on a 4:3 screen using a standard lens
(chosen with the basic calculation).
The DMD™ accurately fills the width of the screen; however, the pillarboxing is
now part of the projected image and is transferred to the screen.
The DMD™ does not fill the height of the screen, which has caused letterboxing -
further blank spaces at the top and bottom of the screen.
The image is now surrounded by blank space, which can be removed if the throw
ratio is increased.
Fig. 3 shows the image projected on the same screen with a lens chosen using
TRC. The increased throw ratio has allowed the 4:3 image to fill the 4:3 screen
seamlessly.
Reference Guide
CHOOSING A LENS
Fig 1
Fig 2
Fig 3
Digital Projection Ltd. M-Vision WUXGA Series
Notes
TRC can only be applied
if greater than 1. If TRC is
1 or less, disregard it and
calculate the throw ratio
using the basic formula..
Rev A January 2024
page 103
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