Section 7 – Calibration
RadianceXD/XE
rev 06/21/11
31
•
Grayscale calibration adjusts the “color of gray” so that the color “gray” adheres to industry
standards (D65 point for color images), at all levels from black to white.
Gamma is the response curve between black and white and also has an industry defined standard
that should be followed. Lumagen has developed a unique 2,5,11,12 or 21 point parametric
grayscale/gamma calibration feature, which allows both grayscale and gamma to be optimized over
the entire range from black to white, and not just at one or two points. The command is:
MENU
→
→
→
→
Output
→
→
→
→
CMS’s
→
→
→
→
[CMS]
→
→
→
→
Gray/Gamma
→
→
→
→
OK
•
The Gamma Factor adjusts the gamma of the video output up or down. Since the Radiance is in
the middle of the video chain, its default goal is to not affect the image Gamma and so the default
Radiance gamma is 1.00. Changing the Gamma Factor allows the Radiance a “coarse correction”
control for display Gamma. It should be set to (Desired_Gamma / Measured_Gamma). The
command is:
MENU
→
→
→
→
Output
→
→
→
→
CMS’s
→
→
→
→
[CMS]
→
→
→
→
Gamma Factor
→
→
→
→
OK
•
After completing the output calibration, copy the results to all configuration memories. The
command is:
MENU
→
→
→
→
Output
→
→
→
→
Copy
→
→
→
→
OK
•
It is a good idea to save the configuration before proceeding. The command is:
MENU
→
→
→
→
Save
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Save
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→
→
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OK
→
→
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→
OK
Iterate the gamut and grayscale/gamma calibrations
•
Since the gamut and grayscale/gamma calibrations interact to some degree, it is important to
repeat both until good results for both are achieved. Note that the following step, color/hue, also
interacts with these controls.
Calibrate Radiance output color and hue
•
If gamut, grayscale/gamma have been calibrated using a color probe, or spectral radiometer, and
the display suffers from red-push, green-push, or blue-push, the Output Configuration color and
hue controls can be used to correct the resulting errors in flesh tones.
•
If no gamut or grayscale calibration has been done, color and hue, and color/hue offsets can still
be used to improve color fidelity using colorbar patterns and color filters. It should be noted that
color filters are not ideal and so whenever possible gamut, grayscale/gamma and color/hue should
be calibrated using a color probe or a spectral radiometer as noted above. Set the Color (
Color
)
and Hue (
Hue
) controls in the Radiance output menu using a colorbar pattern and a blue filter.
The procedure used to accomplish this is described on DVD test discs such as AVIA. Next set the
red color (
Color Red
) and Hue (
Hue Red
) offsets using a red colorbar pattern and a red filter.
Finally set the green color (
Color Green
) and Hue (
Hue Green
) offsets using a green colorbar
pattern and a green filter. Set the menu mode to “service mode,” select Radiance color-bar pattern
with the menu command. While the pattern is displayed, pressing menu leaves the pattern up and
directly selects the color/hue menu. The command is:
MENU
→
→
→
→
Other
→
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→
Test Pattern
→
→
→
→
Adjustable
→
→
→
→
[select pattern]
→
→
→
→
OK
MENU
→
→
→
→
Output
→
→
→
→
CNS’s
→
→
→
→
[CMS]
→
→
→
→
ColorDecoder
→
→
→
→
OK
Iterate gamut, grayscale/gamma and color/hue calibrations.
•
Since the gamut, grayscale/gamma, and color/hue calibrations interact to some degree, it is
important to repeat all three steps until good results for both are achieved.
Calibrate Radiance input overscan, black, white, color and hue
•
The Lumagen provides four independent input configuration memories for each input, MemA
through MemD. Calibration for each input is independent of the other inputs and multiple
independent calibrations can be done for each input. One use for the multiple calibrations for each
input is to calibrate MemA for day and MemB for night viewing. Also, each input memory has
separate calibrations for each of eight input resolutions [See the Memory Configuration section].
Typically the DVD, or Bluray, input is calibrated first, using a DVD, or Bluray, calibration disc, or
you can connect a video test pattern generator. Then the results of this calibration are then copied
to all input memories as a reference starting point for the other sources. However, any source can
be calibrated first if you prefer.