Light is composed of sub-atomic particles named photons. They are positively charged particles of energy that travel at 186,000 miles per second and at different wavelengths, a few of which are discernable to the human eye. However most are not. Visible light travels at wavelengths between 400 nanometers and 740 nanometers. A nanometer is 1 millionth of a meter, 1/10,000 of a millimeter. The visible light spectrum comprises a very minute portion of the full spectrum of light. If you remember the good old Mr. ‘ROY G. BIV’ from school days (red, orange, yellow, green, blue, indigo and violet) then you are familiar with the colors in the visible light spectrum. The table below shows where, within the visible color spectrum, the various colors that we can see are located.
Below about 400 nanometers lie the ultra violets, X-rays and gamma rays. Above 740 nanometers are the infrareds, radar and radio waves. These ‘ultra-visibility’ light waves may be captured on film. However, if they do not fall within the range of light that the human eye detects naturally then they are invisible on normal film and to the human eye as well. There are some exceptions to this rule that we will make mention of soon.
Everything has pigments, little pieces of light reflecting material that correspond to a specific wavelength within the color spectrum, whether visible or not. An object that has purple pigmentation reflects red and blue wavelengths of light. An object that has green pigmentation reflects light that falls within the wavelength of green light, and so on.
Table 2: The Color Wheel
In photography, as well as in other circles, there is a device known as a color wheel. This tool is useful in determining color characteristics. If you can imagine a clock, the color wheel would have red at 12 o’clock, green at four o’clock and blue at eight o’clock. Red, green and blue are the primary colors in the visible light spectrum. There are complimentary colors to these primary colors. The complimentary colors are yellow, cyan and magenta. On the color wheel, yellow is located between red and green at 2 o’clock. Cyan is located at 6 o’clock between green and blue. Between blue and red we have magenta at 10 o’clock. Complimentary colors are relevant in photography for two reasons. First, in a color photographic negative, a blue object will appear yellow, a red image will appear cyan and a green image will appear to be magenta, hence a negative image. Also, in using contrast control filters in black and white photography, a red filter would be used if a red object was to be brightened or objects of green, cyan or blue to be darkened. The red filter would allow red light to pass through, at the same time blocking its complimentary color and other colors near it on the color wheel. We will discuss filters later on in greater detail.
You might ask, ‘Why should I bother to learn about colors if I am shooting black and white film?’ The answer is simple. You are not photographing colors, even with color film. You are photographing light. Photons do not have coloring. That is what pigmentation of matter is for. However, you cannot see light without seeing color and knowing the effects of light and color on film can save a deadline or prevent months, even years of trial and error before getting it right, if at all.
Let's look at light in its true, well, light. Light is a form of energy as is sound and other forces. This energy travels through space in the form of waves. Just like ripples in a pond, these waves leave their source and travel the path of least resistance. Some waves travel faster, such as photons (light). Others travel much more slowly, such as sound waves. The closer to the source, the stronger or bigger the waves tend to be. The further the waves are from their source, the more diminished they are. Imagine that pond. Throw a rock into it and the splash and immediately resultant waves are, comparatively, violent and huge. As the waves travel out and away from the location of the splash they become much smaller. This is a matter of the s or the amplitude, of the waves.
The same analogy can be translated into light. This analog relates to brightness in an image. Turn on a car headlight and an object located five feet in front of it is llluminated very brightly. Train those same headlights on a subject 100 feet distant and it is much more dim. The same happens to the subject in front of you and your camera. The more intense the light on the subject, or the greater the amplitude of those light waves, the brighter it will appear. And the converse is true: less amplitude equals a more dimly lit subject. THIS IS WHAT YOU PHOTOGRAPH IN BLACK AND WHITE PHOTOGRAPHY.
The ability to record color is not present in the emulsion so all you can do is to photograph differences in light amplitude or levels of contrast. Without color, a photograph relies entirely upon contrast and line and shape to draw the viewer's attention. And it is the ability to make your gear translate this light into the images that you produce that make all the difference in the world.
The other characteristic of energy we will discuss here is wavelength. As mentioned above, all energy travels not only at different strengths but at different wavelengths as well. Imagine the ocean or a large lake during a storm. The waves crash ashore in succession. Sometimes the waves follow more closely and at other times they are spread out from each other. The distance from the crest of one wave to the crest of the next is the wavelength. Kinetic energy (energy in motion) travels in waves. Sound travels in varying wavelengths so we are able to make out the difference between the hum of a refrigerator and the sound of a car's horn or between the voices of your son and your wife. Visible light, as well as all light, travels at different wavelengths as well. The wavelength of red light is about that of blue light. This is why you are more prone to have your attention drawn by a brake light or a stop sign than by a blue mailbox on the side of the road. Red is stronger and travels at a much narrower wavelength than does blue light.
It is best to know your enemy. And by getting to know light, it can be your closest ally.
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