Understanding photography requires an understanding of art and science. The word photography comes from the Greek “to paint with light.” So in order to create art with photography means you have to understand how light works.
Light is a form of radiation that has been studied by scientists for hundreds of years. Two theories have been around for hundreds of years: quantum theory and wave theory. Quantum theory states that light moves in a single direction. Wave theory also believes that light has wave lengths like sounds. These wave lengths move in vary small oscillations (measured in nanometers). The visible light rang moves from 400-700nm.
Eventually, the two theories were reconciled into a unique quantum wave theory. This makes light unique in many ways.
Another characteristic of light is that, in a vacuum, light travels about 186,000 miles per second. I say “in a vacuum” because when light travels through different mediums, it changes speed. The best example I have is to imagine what it is like to walk through an empty room and then how much more difficult it is to walk through water.
When light moves through a camera lens, the speed of the light changes, and if the glass is given specific shapes it will bend as it moves through the glass. When the light re-enters normal air, it resumes it previous speed and continues on its way.
This is how a lens is able to bend the light (refraction) to capture the light on the focal plane (the flat area that captures the image on the film or computer chip).
The color of light is determined partially by the bandwidth frequency. The longer the wave length the warmer the color: Red sits closer to the 700nm wave lengths. Blues and violets are on the other end of the spectrum in the 400nm area. The color spectrum breaks out exactly like the colors of the rainbow (remember R.O.Y. G. B.I.V.?).
Light itself does not have a color. The band width frequency must first react with a material and then bounce back to the eye. Even the blue in the sky is a reaction of the moisture in the air that our eyes register.
The blue color has a tighter wave pattern and reaches our eyes with more energy than the slower frequencies of red. However, as the sun lowers to the horizon, the distance between the sun and our eyes has more atmospheres to work through. By the time the light hits our eyes only the lower frequencies meets our eyes and that is why we see a warm red, orange and pink sunsets.
When light hits a surface, the material will absorb certain frequencies and reflect others. So when you see a green cloth, you are really only seeing the light that is reflected. The red and blue light is absorbed by the cloth.
Light is effected by a medium in three ways: reflection, absorption and transmission.
Now that we understand that light is a linear wave length. It is time to start understanding how to a photography practically deals with light.
Color Balance—Each light source is transmitted at a different light frequency. That means that not all light is white. The sun at noon is about as white as you can get naturally. The sun at sunset is red. The light is different in incandescent light bulbs and fluorescent lights.
Photographers need to know how to measure the light in order to know how to deal with it. The most convenient way to describe color is by degrees Kelvin. Degrees Kelvin is a measurement of whiteness (i.e. the amount of pure light).
Kelvin is a measurement of heat. Zero degrees Kelvin is equal to -273 Celsius. If you are wondering why that number, well that is because at -273 Celsius is absolute zero. Nothing can get colder than zero degrees Kelvin. That also means that all light is absorbed and anything that is zero degrees Kelvin is absolute black.
If you have every seen a piece of metal heat up, you will notice that it changes color. The hotter it gets the more it starts to glow. At first it will glow red. Eventually it will glow blue and then white. That color can be measured in degrees Kelvin.
Daylight, or pure light, is approximately 5000-5500 degrees Kelvin. An incandescent bulb burns approximately 2000 degree Kelvin. Fluorescent lights can be 3500, 4500 and 6500 degrees Kelvin.
If your camera has precise color balance control, it will probably allow you to adjust both the default settings (incandescent bulb, fluorescents, daylight, cloudy day, and flash) AND your camera will also have the ability to adjust the specific Kelvin temperature.
Color Relationships—Color and Light can also be defined by its three qualities: hue, brightness and saturation.
Hue is the actual color (or wave length) reflected by an object. The primary colors are red, green, and blue (remember the rainbow?). There are also complimentary colors, which are even mixes of each of the primary colors. These colors are cyan, magenta, and yellow. Many photographers represent these colors in a wheel. This makes it easier to see the association of colors.
Brightness is the color of the light independent of its hue. This means you can have a bright blue and a dull blue. Think of adjusting the brightness on your monitor. Even though you can make the screen brighter and darker, the hue remains the same.
Saturation is the degree of black and white that is added to a hue. Think of it like mixing a color with paint (white and black).
Understanding these fundamentals are important to a photographer. It will allow you to learn how to adjust the color balance of your film or digital camera. Understanding how light works will also help you later on when you are crafting light for specific effects.