NewTek TriCaster Advanced Edition User Guide - Manual (Page 318)

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C.2 CALIBRATING VIDEO SOURCES
The obvious disparity between neighboring televisions on display in a store amply demonstrates that even
identical (and brand-new) video devices can differ dramatically. When mixing multiple cameras we need to
ensure that their output matches. Switching to a camera with obviously different color characteristics will
be seen as a glaring error by your viewers.
Even when we restrict matters to a single unit, color characteristics can change as the system warms up, and
as it ages. For this reason, it’s important to allow a device to warm up before attempting to calibrate it.
C.2.1 SETTING BLACK AND WHITE
Naturally, the color range available for transmission and recording is bounded at the upper level by white
and at the lower level by black. Anything else falls somewhere in-between.
Consider what happens if you gradually raise the brightness control on your television. Beyond a certain
point (and unlike claims made for laundry detergent) your whites do not become whiter. They can’t – the
upper limit (white) is firmly fixed. Instead, parts of the image that are nearly white are boosted, eventually
also becoming white. Meanwhile, black portions of the picture are tending towards gray. Since white cannot
become whiter, and black has become gray, we could say that the dynamic range of the image has been
narrowed. The net result is a less vibrant image.
The same thing is true for video from your cameras. If the black and white levels from the camera are
incorrect, you are effectively losing either shadow or highlight detail. For this reason, the first thing many
do is calibrate their camera for correct levels.
W AVEFORM M ONITOR
From days of old, for video engineering purposes the scale between black and white was defined in IRE units
(IRE being an acronym for “Institute of Radio Engineers”). White was pegged at 100 IRE. For PAL (and
NTSC-J) countries, black was defined as 0 IRE. For NTSC lands, black properly sat at 7.5 IRE.
Thankfully, the day of strict adherence to these analog video concepts has virtually disappeared. Today,
confirming that the black and white levels your camera is sending TriCaster are correct is as simple as
sending first black, and then white (or the brightest past of your scene, and reading values from the scale
alongside TriCaster’s Waveform scope.
Hint: TriCaster automatically compensates for the traditional 7.5 IRE black (also known as “setup” and “pedestal”)
in SD format NTSC sessions.
Connect your camera to the correct TriCaster input, block the lens so it receives no illumination, and check
the level shown in the Waveform monitor. Generally, it should be 16 on the 8bit scale.
To check white, use either the brightest part of your scene or a white card, ensuring that it is evenly
illuminated with the same lighting your main subject will receive. Move in or zoom to fill the viewfinder with
this, and confirm that the Waveform monitor is showing 235 on the same scale. Otherwise, you might try
using your camera’s Auto White Balance feature with the white card – your camera manual will provide
instructions. Afterwards, check the black level again.