digital media lecture 7: color part 2 georgia gwinnett college school of science and technology dr....
TRANSCRIPT
Digital Media
Lecture 7: Color part 2
Georgia Gwinnett CollegeSchool of Science and Technology
Dr. Jim Rowan
Refer to Supplemental text:
You have a blue ball and walk into a room lit with a red light. What color is the ball while in the room?
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Color Models other than RGB
CMYK– cyan– magenta– yellow– key (black)
HSV, HSB, HSL– Hue– Saturation – value. brightness, lightness
Colored light shining on a white surface
One red light, one blue light and one green light…
Arranged to overlap… Creating Cyan, Magenta and Yellow and… White
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Cyan = Green + BlueCyan = White - Red
Yellow = Red + GreenYellow = White - Blue
Magenta = Red + BlueMagenta = White - Green
This color model can be used as an Additive model appropriate for use with light
This color model can also be used as a Subtractive model appropriate for use with ink and paint... things that absorb light
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White = Red + Green + Blue
white paper
white paper cyan ink
magenta ink
white light
removes green
removes redwhite light
white light
removes green
removes red
leavingblue light
magentaleaving
light
magentaleaving
lightcyanleaving
light
CMYK model
Cyan Magenta Yellow Key (black)
– While you should be able to make black by mixing Cyan, Magenta and Yellow…
– Paint (and ink) is not perfect
Subtractive model Used by the printing industry
HSV model
Another way of looking at color Hue
– The color described as degrees from red Saturation
– How pale the color is– Think of it as adding white to the color
Brightness– How intense the color is– Thinks of it as adding black to the color
Adjusting the Hue
Adjusting the Hue
Adjusting the Hue
Adjusting the Hue
Adjusting the Saturation
Adjusting the Value
Full-On Red in RGB model
Full-On Green in RGB model
Full-On Blue in RGB model
The transition from B&W to Color TV
B&W just needs intensity changes to make white-gray-black– intensity varies as the electron beam is drawn across the screen
Color is RGB+Intensity for each– could transmit each color with its intensity and it would work for
color tv but– can’t use the same signal model for color because the B&W tv’s
wouldn’t work– Solution: Transmit the necessary color information during the
retrace.– Color is transmitted as luminance and two colors– B&W tv’s simply ignore it because the beam is off
RGB RGB RGB
RGB RGB RGB
RGB RGB RGB
B B B
B B B
B B B
G G G
G G G
G G G
R R R
R R R
R R R
• Allows the use of the brightness and contrast of each individual color to be manipulated using levels and curves
• Allows a very fine level of control
• Very time consuming• Color balance, hue and
saturation adjustments on the whole image is a shortcut
RGB
Channels
http://en.wikipedia.org/wiki/Channel_(digital_image)
Channels
Red Green
Blue