USL PSA-200U - Manual (Page 11)

Page 11 1st Edition. October, 2004 USL, Inc. PSA-200U Instruction Manual
Using the Spot Meter
The Spot Meter function is useful in taking
measurements of ambient light, reflected
light and lens flare. While in Camera View
(F3) or Luminance (F4), press F6, or click on
the Spot Meter icon. Use the mouse to move
to any part of the area being analyzed and
the luminance value displays in the status
bar at the bottom of the screen, along with
the center luminance and the number of the
zone the Spot Meter is in (see Fig. 5).
(Fig. 5) Spot Meter
Checking Weave and Jitter
(Optional Feature)
The PSA-200U measures picture steadiness
in terms of Weave and Jitter (or Jump).
Weave is the residual horizontal motion
of a projected image. Jitter is the residual
vertical motion of the image. The software
uses the image of the SMPTE test film RP
40 for calibration and measurements. (For
information on measurements and accept-
able values, please refer to SMPTE Recom-
mended Practice # RP1-5-1995. The width of
one square on the test pattern represents
0.5% weave. The vertical dimension of a
square represents 0.94% jitter when the
aspect ratio is 1.85 to 1.)
Procedure
1. The loop of RP-40 test film should be
as long as practical. It is good practice
to use a loop of 20 to 25 feet in length,
passing the film from the projector to
a platter roller and back. The minimum
practical loop length is about eight
feet. Shorter lengths result in too short
a time interval between splices for
accurate measurements to be made.
The algorithms of the weave and jit-
ter measurements are iterative and
averaging processes. They analyze
the change in position of the squares
as the film passes through the gate.
The wide misalignments of a splice
cause errors which must be evaluated
and discarded. The longer the time
between splices, the higher the per-
centage of good data that is available
for the analysis.
2. Use the “flat” lens of the projector,
(1.85:1 for example), and enter the
aspect ratio of the aperture in the
“Program” set-up box of the “Settings”
menu.
3. Position the camera approximately
one screen-width back from the screen
in the audience area of the auditorium.
Center the screen image on the view-
finder.
4. Run the loop of RP-40 test pattern
film.
5. Press F3, or click on Camera View.
Make sure that the RP40 test image is
centered in the Camera View presenta-
tion (see Fig. 6).
(Fig. 6) SMPTE Test Pattern