Color. Light vs Paint: Additive, Subtractive, Tradtional and the 7 Colors of the Rainbow.
When I grew up, i learned there was 7 colors to the rainbow, red, orange, yellow, green, blue, indigo and violet. When I got older, it was very confusing mixing primary colors; where was the indigo? As it turns out there is a great deal more to color than the obvious and what you know about color is then the opposite when going from water colors to a computer screen.
Color can be confusing, especially when the primary colors shift from RGB to CMY. why do they shift? Are you talking about additive color? (RGB primary colors) or subtractive? (CMY) or traditional additive color? Or perhaps, physical pigments vs light (from the sun, light bulbs or computer screens)?
For LIGHT,
combing equal amounts of RGB additive primary colors,
creates pure white. the secondary colors, in this case, are Cyan (from Blue & Green), Magenta (from Blue and Red) and Yellow (from Red and Green).
RGB: Red Green Blue
CMY: Cyan Magenta Yellow
For LIGHT,
the Subtractive primary colors are CMY, Cyan, Magenta and Yellow. here, the secondary colors, for light, are Red (from Yellow & Magenta), Green (from Yellow & Cyan), and Blue (from Cyan & Magenta). Removing these primary colors creates white and combing them together, in equal amounts, gives you black. The black is key for print. CMYK, the subtractive primaries for light plus K for blacK, are used in ink, for the printing process. CMYK are true colors, used for either desktop ink jet printers or industrial grade printing presses.
You can easily test this in photoshop by creating pure colors with the color slider. Increase red to max (255), and reduce green and blue to 0, to create pure red. then create pure green and pure blue. add these together in pairs, with blending modes, to create the secondary colors (Cyan, Yellow, and Magenta accordingly). now add all three together. try it, seeing is believing.
Red slider in Photoshop
Green slider in Photoshop
Blue slider in Photoshop
For PHYSICAL PIGMENT/ PAINTS,
the Traditional primary colors are Red, Yellow and Blue.
combing Red and Yellow creates secondary color Orange; Yellow and Blue, make Green; and Blue and Red, make Purple/Violet. This is where the color wheel comes into play. The color wheel, from any art supply store is the "traditional additive color wheel," with Red, Yellow and Blue primary colors. You can special order a subtractive CMY color wheel, but they don't carry it in most stores because it is too confusing for people who never use photoshop.
So what about the 7 colors from childhood? As it turns out, Isaac Newton created the seven colors, even claiming 7 colors came from sunlight being split or "refracted" from a prism. Unfortunately, Newton took observable science and fit it into his beliefs, 'Age of Enlightenment,' etc. It’s a good thing he didn't do that for calculus or gravity :)
I hope this helps clear up a few things.
GS FORD
Pe
Photographic elements