LESSON 2: COLOR THEORY & COLOR MANAGEMENT
These are the things every visual artist MUST know and understand.
LIGHT & COLOR
If you want to learn to manage color, it helps to first understand just what it is:
Color is a property of both an object and light, and it originates in the eye or the brain of the observer. In other words, color is an event that occurs among three participants: a light source, an object and an observer (Color on Wikipedia).
Light is part of the electromagnetic spectrum, and the human eye is only sensitive to a small range of wavelengths near the middle of spectrum. When radiation in this visible part of the spectrum strikes the eye, the brain senses light and color (Light on Wikipedia).
Most camera sensors and films are manufactured to respond to about the same range of wavelenghs that the eye can see, but some of them can also respond to ultraviolet and infrared radiation.
To make the best use of color’s expressive possibilities, you need to understand some of the science of color and its psychology.
COLOR WHEEL & COLOR MODES
All colors can be created by mixing three primary colors.
The Additive color system primaries: RGB (Red, Green, Blue) is the mixing of red, green and blue points of light in varying proportions to produce any color on computer and television screens.
CMYK (Cyan, Magenta, Yellow & Key = Black) is a Subtractive color model, which explains the mixing of paints, dyes, inks, and natural colorants to create a full range of colors, each caused by subtracting (that is, absorbing) some wavelengths of light and reflecting the others.
Therefore: choose RGB, the additive color system, for your on screen images and CMYK, Subtractive color model, is for your prints (check with your printing lab!).
CMYK can’t reproduce all of the same bright colors as RGB, that’s why it takes knowledge and experience to make sure your images look identical on screen and in print.
RELATIONSHIP WITH THE SPECTRUM + TRICKY TRICK
Why RGB and CMYK are always written in that order (not GRB or YCKM):
- The colors of the spectrum are usually listed in order of increasing frequency: red, orange, yellow, green, blue and violet – ROYGBV;
- The additive primaries divide this spectrum roughly into thirds, corresponding to reds, greens and blues. So ROYGBV leads to RGB;
- We write the subtractive primaries in the order that matches them to their additive counterparts (their opposites), thus RGB leads to CMY (K=black).
You may find this handy for remembering complementary colors. For example, if you’re working on a CMYK image with a blue cast, and need to compensate: just remember RGB/CMY, so Red is complementary to Cyan, Green to Magenta, and Blue to Yellow.
In other words, when you add Yellow, Blue will be subtracted, and vice versa. Same applies to the rest of the primaries.
ONE MORE TRICK
When you need to quickly find the opposite or complementary color to one you’re using, sample your color (hold Option (ALT) when working with the Brush tool, or use the Eyedropper tool) and get into the Color Picker menu. Add or subtract 180 from the H number in the H (hue), S (saturation), B (brightness) values.
THE OBSERVER: HUMAN EYE
The human eye has three types of color sensors (corresponding roughly to red, greens and blues) and that’s what lets us reproduce colors at all using just three pigments on paper, or just three phosphors in a monitor (Human Eye on Wikipedia).
The retina is a complex layer of nerve cells lining the back of your eye. The nerve cells in the retina that respond to the light are called photoreceptors, and come in two types: rods and cones (due to their shapes). Rods provide vision in lower light conditions and are color-blind, and cones respond to color and tone, and function in bright light conditions. According to Harvard neurobiologist Margaret Livingstone, the visual brain processes tonal information separate from color.
On top of that, our brains make us believe that local colors and tones are stable and unchanging. For example, if we look at a green car lit by the orange sunset light or fluorescent garage lights, we still believe it’s green. Our visual system constantly makes such inferences, and it’s almost impossible for our conscious minds to override it.
Here are a couple of visual examples:
In the Checker shadow illusion published by Edward H. Adelson, Professor of Vision Science at MIT, the squares marked A and B are the same shade of gray, yet they appear different. It happens because our visual system tries to determine where the shadows are and compensate for them. And it all happens without our conscious control.
However, when the A and B squares are isolated from the surrounding context, the effect of the illusion is dispelled.
If you are still in doubt, you can download these images and compare the color of the squares A and B by using the Eyedropper tool in Photoshop.
Here’s what happens when we’re tricked by our visual system when we look at colors:
Similar tricks our visual system plays on us when we look at James Gurney’s Colored Cubes illusion. The context of the picture makes us believe that the squares A and B are of different colors, when in fact they are of the same neutral gray color. That becomes obvious when we place both squares side by side:
As you can see, it is possible to switch off the context cues and see the real colors. For that we need to, firstly, be aware of the constant guesswork that’s happening in the background of our visual perception, and, secondly, learn to mentally or physically isolate colors that we’re trying to evaluate in a picture or reality.
Color systems divide all colors into three measurements: hue, value and saturation.
Hue is the most intuitive of the three, it is what we normally name the colors of objects: a green car, a red apple.
Value (sometimes called Lightness or Luminance) is a measure of the brightness or darkness of a color or the gray that would be left if the color hue was removed. Two different colors can have identical value.
Saturation – the purity, vividness or intensity of a color.
COLOR BALANCE & COLOR TEMPERATURES
Accurate color in your photographs comes from a close match between the color temperature of the light on your subject and the color balance of your film or digital sensor (i.e. White Balance in DSLR cameras). In photography, color balance is the global adjustment of the intensities of the colors. An important goal of this adjustment is to render specific colors – particularly neutral colors – so that they appear correct or pleasing in the image.
Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, and other fields, and is conventionally stated in the unit of absolute temperature, the kelvin, having the unit symbol K. Color temperatures over 5,000K are called cool colors (blueish white), while lower color temperatures (2,700–3,000K) are called warm colors (yellowish white through red). Yes, a little confusing, at first: higher Kelvin temperatures cause cooler colors, and lower Kelvin temperatures cause wamer colors. Kelvin temperatures cause warmer colors.
If the White Balance setting on your camera is incorrect at the moment of capturing an image, you will recognize that by a slight or strong colorcast (in most cases blue or yellow). Don’t worry it is still possible to save your image, especially if you shoot in Raw format. Chances to ruin an image with an incorrect White Balance setting are much higher when shooting in JPEG format. Simply get things right in camera as you shoot.
Oh, and always shoot in Raw!
Color Management & Color Spaces article here: www.retouchingacademy.com/color-management
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