4 - Color Mixing. S pectral P ower D istribution (SPD). Perfect absorber at all wavelengths = “Blackbody” (if T = 0 K). Blackbody with T = 3000 K. Units? W/(m 2 Hz steradian) W/(m 2 m ster) W/(m 2 m ster) W/(m 2 nm ster) etc. Color Perception & Color Mixing. Hue – the color
Spectral Power Distribution (SPD)
Perfect absorber at all wavelengths = “Blackbody”
(if T = 0 K)
W/(m2 Hz steradian)
W/(m2 m ster)
W/(m2 nm ster)
What does the human eye see when mixing roughly “equal” amounts of Red, Yellow, Green, Cyan, Blue, and Magenta?
G + R = Y
B + R = M
B + G = C
B + G + R = W
(unequal amounts will produce other hues)
Any 3 colors that add up to make white light can be “primary” colors, but RGB seems to produce the widest range of other colors, so we usually refer to them as THE primary colors for additive mixing of light.
M + Y = (B + R) + (G + R) = (B + G + R) + R = W + R
originally contained red, orange, yellow, green, blue, indigo, and violet.
Partitive Mixing - close spatially
Visual Persistence - close temporally
(paints, filters, “what’s left?”)
Result of passing light with a given SPD through a filter (or series of filters):
Filter Types (or series of filters):
Kodak Wratten 44A Filter (or series of filters):
We see this but not this
Spectral “Purity” (or series of filters):
Sun with“H” filter, = 656.3 nm, R~10,000
Neutral Density Filters - These have “flat” transmission curves, or R << 1
Building colored images from filtered ones (or series of filters):
Colored Pigments (Paints) (or series of filters):
Relies on combinations of additive and subtractive color mixing.
When layered, can depend in transmission, reflection, partitive color mixing, etc.