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Presented by Mike Waidson
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Agenda
Understanding color and human vision
Color Correction
Gamut Monitoring
Understanding Diamond Display
Introduction to the New Spearhead Display
Composite Gamut Monitoring using Arrowhead Display
Content Quality Assurance
Color and Gamut Monitoring2
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Basic Anatomy of the human vision system
http://webvision.med.utah.edu/index.html
3 Color and Gamut Monitoring
Physical part/elements
Eye, Lens and Retina Rods
Sensitive to Blue-green light
Used for vision under dark-dim
conditions.
Cones 3 Types of Cones
Sensitive to either
long wavelengths of light (red light)medium wavelengths of light (green light)
short wavelengths of light (blue light)
Optic nerve
http://webvision.med.utah.edu/imageswv/3cone.jpeg7/27/2019 WebinarGamut
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Color Model developing color spaces
CIE 1931 XYZ color space with 2% observer is still foundation of most
color models
Trichromatic stimulus (color value)
Lightness decreases towards not shown third dimmension
Saturation inceases towards edges
Black
White
4 Color and Gamut Monitoring
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Color Correction
Primary Color Correction Focuses on Overall color correction of image.
Secondary Color Correction Focuses to enhance specific areas or components of the image.
Are used to change colors after shooting
Mostly used to enhance the message of an image by highlighting areas,
changing the tonal range of a particular area etc.
Key areas: Skin tone, sky, grass. Making it look real
Color and Gamut Monitoring6
Secondary Color CorrectionPrimary Color Correction
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RGB and YPbPr Color space.
YPbPr color cube shows Parallel-Piped of RGB colors Certain YPbPr values when converted to RGB will fall outside the
allowed range and will be out of Gamut
Color and Gamut Monitoring7
RGB Color Cube YPbPr Color Cube
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Gamut monitoring - The traditional way RGB domain
Color and Gamut Monitoring8
Maximum
Gamut
Minimum
Gamut
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How the DiamondDisplay is constructed
Color and Gamut Monitoring9
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Gamut monitoring Diamonddisplay
Configuration Menu
Selectable Gamut Thresholds
Gamut
Limits
Color and Gamut Monitoring10
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Diamond Display - Live Signal Gamut Errors Blue
11 Color and Gamut Monitoring
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Diamond Display - Live Signal Gamut Errors
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Diamond Display - Live Signal Gamut Errors
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Diamond Display Live Signal Corrected Gamut
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Diamond Display Camera Balancing
Black Center
White Outer
Apex
White Outer
Apex
15 Color and Gamut Monitoring
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Diamond Display Camera Balancing Red Error
Deviation from
verticalindicates color
balance error
In this case a
Red Gain
Error
Deviation from
center
indicates color
balance error
Black Offset in
Red Channel
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New Spearhead Display
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Can we make a new display that has metrics ofSaturation, Value and Lightness?
RGB gamut space as XY plot of
max(rgb) and min(rgb)
100%
100% 0%
0%
100%white
max(rgb)=m
in(rgb)
monochrom
eaxis
max(rgb) < min(rgb) triangle
(impossible)
max(rgb) > min(rgb) triangle
valid RGB space
50%
50%
min(r,g,b)
max(r,g,b
)
Simple linear rotation to make monochrome
axis vertical.
max(rgb)+min(rgb)
2
max(rgb) - min(rgb)0%
color-bars
black
black
color-bars
white
100%
50%100%
50%
valid RGB space
inside triangular area
monochrome
axis
max(rgb)=100%
min(rgb)=0
%
rotate 45 deg
(lightness)
(non-normalized
saturation)
Premise:
1) For gamut limit testing we are interested in the max and min values of R, G, and B.
2) Artistic metrics like Value and Saturation are functions of both max and min of R, G, and B.
Color and Gamut Monitoring19
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New Spearhead Display(Color Lightness, Saturation and Value)
X(i) = max(i) - min(i)
Y(i) = [max(i) + min(i)]/2
50%
75%
25%
100%
75%
50%
25%
Valu
e
Saturation(HSV)
Lightness
black
white
mono
chromeaxis
50%
100%
25%
102% (limit)
0%
-0.5%
105%
Spearhead triangular RGB Gamut space:
max(i) = maximum of r(i), g(i) , b(i);
min(i) = minimum of r(i), g(i) , b(i);in mV.
The space is bounded by 3 lines:
1) the vertical line (monochrome) where
max(i) = min(i),
i.e. Y(i) = max(i) = min(i), X(i) = 0;
2) the line of all possible 100% Saturated
colors where min(i) = 0, max(i) = 0..700mV
i.e Y(i) = max(i)/2, X(i) = max(i),or graphically the y = x/2 line;
and
3) the line of all possible 100% Value colors
where max(i) = 700mV, min(i) = 0..700mV
i.e Y(i) = 700mV/2 + min(i)/2,
X(i) = 700mV - min(i),
or graphically the y = -x/2 + 700mV
Note:All valid rgb values (r(i), g(i), or b(i)within the range 0.. 700mV) are contained
within the Spearhead triangular gamut
space. All invalid (or illegal) rgb values
(min(i) < 0, or max(i) > 700mV) are outside
the Spearhead gamut space. Adjustable
gamut limit detector thresholds are indicated
as graticule markers (i.e. -0.5% and 105%).
Color and Gamut Monitoring20
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How to Make Gamut MeasurementUsing Spearhead.
Select one of the tiles
1,2,3 or 4
Select Gamut button
Push and Hold Gamut to
bring up the menu
Use arrow keys or general
knob to select Spearhead
display.
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Rainbow (variable Hue) Test Pattern
100% Value
100% Sat
text
monochrome
monochrome
Color and Gamut Monitoring22
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Rainbow Patternwith SMPTE Pb/Pr Hue rotation (RGB gamut error)
Color and Gamut Monitoring23
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Rainbow Patternwith Color Corrector Green Gamma Adjustment Error
Color and Gamut Monitoring24
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Spearhead for Content Quality Control(RGB gamut limits)
Fold Diamond Horizontally and Vertically to form Spearhead
The Spearhead display indicates Out-of-Gamut RGB components (triangle boundary) Spearhead also indicates how much the Signal is OVER Saturated or OVER Value (or
BOTH) so that we can see what has to change to correct the signal back into gamut.
This way a better trade-off of reducing Saturation or Value (or both) without affecting
the Hue can be accomplished with the least compromise in artistic quality.
Color and Gamut Monitoring25
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Using Spearhead with a Color Corrector
100%
black
white
100%
0%
Adjust Setup
Adjust Chroma
Adjust Gamma and
gray-scale tracking
Adjust RGB Gain
Push back to monochrome
line with RGB gamma controls
Adjust RGB Black Level
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Image with Gamut error in Blacks and RGB Gain
Color and Gamut Monitoring27
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Image after Color Correction using Spearhead Display
Color and Gamut Monitoring28
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Image Enhancement using Spearhead Display
BeforeAfter
Limited to 75% Value
Negative black level
100% Value
utilizing full
gamut space
No negative blacks
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Composite Gamut Monitoring
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Understanding the ArrowheadDisplay
Luma
Limits
Upper Luma+Chroma
Lower
Luma+Chroma
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Graticules available for both PAL & NTSC
PAL Graticule
Keep trace within graticule
NTSC Graticule
Keep trace within graticule
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Arrowhead Display Live Signal
Keep trace within graticule limits of Arrowhead
Adjust Luma and black level controls for vertical adjustment
Adjust Chroma controls for horizontal adjustment
33 Color and Gamut Monitoring
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Arrowhead Display vs Pseudo Composite Live Signal
Keep trace within graticule limits
Saves having to view Waveform and Vector displays
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Content Quality Assurance
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Tape QA
Video Session and Error Log provide a simplify the QA process
After program has been edited QA of Incoming program
QA of Duplication
Video Session
Provides summary of video
Error Log Reports errors based on Alarm settings
Provides log related to timecode
Allows easy navigation to errors
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Video Session
Provides Summary of Video
signal during session
Simple indication of Gamut
Errors
Lower case letters indicate
values go below threshold
Capital letters indicate value
exceeds threshold
In this case
Lower r,g,b & l indicate valuesare below threshold for this
SMPTE bars test signal
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Error Log
Provides log of
errors Related to
timecode
Internal time
of day
Simplifies QAprocess
Log can be
printed
via network
interface
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Conclusion
Important to ensure Gamut compliance
Tektronix Diamond and Spearhead displays can aid in RGB gamutadjustments
Allows user to visualize adjustment made during color correction or
camera balancing
Tektronix Arrowhead display is suitable for Composite Gamutadjustments
The Error Log and session display of the instrument allow operators to
pin point errors within the material
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More Information
Local Sales and [email protected]
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Question Time
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