christopher walrath
07-03-2010, 07:17 PM
Light is composed of sub-atomic particles named photons. They are positively charged particles of energy that travel at an accepted speed of 186,000 miles per second and at different wavelengths, or frequencies, 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 one meter or one 1,000th 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.
The Visible Color Spectrum
nm 360 420 440 460 480 500 520 540 560 580 600 620 640 680 700 720 740 760 780 800 +
Ultraviolet Violet Blue Blue-Green Green Yellow-Green Yellow Orange Red Deep Red Infrared
(Forgive me for the crudity of this scale, it's not exact but you get the point.)
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 or on a digital sensor. However, if they do not fall within the range of light that the human eye detects naturally then they remain invisible 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.
In photography, as well as in other circles, there is a device known as a color wheel.
http://farm5.static.flickr.com/4099/4758438231_cb2f6c0e53_m.jpg
This tool is useful in determining color characteristics. If you can imagine a clock, as in the image above, 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.
This is also useful in digital photography, mostly in post-production. In working with filtration, when you adjust one color up in a level you will effectively lower the complimentary color and its adjacent colors. The converse is ture as well. In lower the values of one color you effectively strengthen the complimentary color and adjacent colors by the changed color's absence.
We will discuss filters later on in greater detail.
One might ask, ‘Why should I bother to learn about colors if I am shooting black and white?’ The answer is simple. You are not photographing colors, even with color film or digital sensors. 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 affects 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. It is best to know your enemy. And by getting to know light, it can be your closest ally.
The Visible Color Spectrum
nm 360 420 440 460 480 500 520 540 560 580 600 620 640 680 700 720 740 760 780 800 +
Ultraviolet Violet Blue Blue-Green Green Yellow-Green Yellow Orange Red Deep Red Infrared
(Forgive me for the crudity of this scale, it's not exact but you get the point.)
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 or on a digital sensor. However, if they do not fall within the range of light that the human eye detects naturally then they remain invisible 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.
In photography, as well as in other circles, there is a device known as a color wheel.
http://farm5.static.flickr.com/4099/4758438231_cb2f6c0e53_m.jpg
This tool is useful in determining color characteristics. If you can imagine a clock, as in the image above, 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.
This is also useful in digital photography, mostly in post-production. In working with filtration, when you adjust one color up in a level you will effectively lower the complimentary color and its adjacent colors. The converse is ture as well. In lower the values of one color you effectively strengthen the complimentary color and adjacent colors by the changed color's absence.
We will discuss filters later on in greater detail.
One might ask, ‘Why should I bother to learn about colors if I am shooting black and white?’ The answer is simple. You are not photographing colors, even with color film or digital sensors. 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 affects 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. It is best to know your enemy. And by getting to know light, it can be your closest ally.