TRU 8 / VideoWin 3 Quick Reference Guide
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In some instances, particularly with very small, high resolution portable displays, the 500mm distance
may be problematic. The goal should be to maintain the 2 degree angular cone of acceptance, if
possible. The standard explicitly states that any deviation from the 500mm measurement distance should
be noted.
Figure 3 Description of various terms from the standard
Confirming the general calibration accuracy of the Imager
Procedure
1. Confirm that ambient temperature and humidity requirements are met
2. Power and warm-up the Reference Source and all instruments for at least 20
minutes
3. Adjust the reference source for correct lamp current and luminance
4. Align and focus the TRU8 on the measuring window of the Reference Source. Make
sure the distance from the front of the lens to the target is a minimum of 10 focal
lengths of the objective lens. For example, the focal length of the MS-60 objective
lens is 60 mm, therefore the recommended distance is 600 mm (1.97 ft.).
5. Measure the Reference Source with the TRU8.
6. In VideoWin software, generate an AOR centered on the measuring window with a
size of at least 330 x 247 camera pixels (1% of total camera pixels).
7. If the measured results do not agree with the published data for the Reference
Source, measure the Reference Source with the spectroradiometer taking care to
match the area sampled by the measuring aperture of the spectroradiometer to that
of the AOR generated in Step 6.
8. If the TRU8 and spectroradiometer agree with each other but do not agree with the
standard, then the issue lies with the standard.
9. If one of the instruments agrees with the standard and the other does not, then the
instrument that disagrees requires calibration.
