LIGHT BASICS :: IS IT TOO HOT IN HERE?
Light.
The most basic, elemental form of energy, light is the most critical element for all forms of life. As photographers, we wrestle constantly with light, whether there is too little, too much, or coming from the wrong direction. Much of the anxiety can be eased by putting more effort to understanding this most fundamental element and its most critical role in creating the pictures we love.
Visible light, what the human eye is capable of seeing, is but a very small part of the eletromagnetic spectrum. The combined fluctuations of electric and magnetic waves transport energy from point A to point B. As light interacts with matter, the wave changes, allowing the human eye to assess the qualities of the matter. These changes in light are what our eyes interpret as color.
We measure light, and subsequently color, in terms of temperature. Without getting bogged down into scientific explanations, the amount of heat emitted from a light source determines its color (with the exception of fluorescent bulbs). These temperatures, measured most typically on what is called a black-body scale, are important in helping us determine what it absolute white. When shooting film, for example, tungsten film recognizes white according to the temperature of light emitted from a tungsten bulb, which is 2800 K. Daylight film, by contrast, recognizes pure white on a range between 5500-6000 K. Using film inappropriate to the light source inevitably alters how the film interprets color. Fluorescent light presents a challenge to photography because the light does not originate with a heat source and therefore varies in temperature, making it nearly impossible to find an accurate point for white balance.
What difference does any of this make?
Consider the challenges of outdoor photography. Experienced photographers will often talk about catching the "magic hour," within one hour after sunrise or one hour before sunset. The reason is because of the temperature of sunlight during those periods of time.
Look at the following outdoor temperature scale:
NOTE: There are six different types of fluorescent lamps, making it virtually impossible to know what the exact white temperature is going to be. Even the best fluorescent filters tend to leave a greenish hue, making fluorescent light a challenge for photography.
If we assume that the professional tungsten lamp temperature of 3200 K is ideal for portrait photography, then once the sunlight temperature exceeds 3500 K, one can anticipate increasingly severe problems as the light temperature steadily climbs. Even overcast skies emit a temperature hot enough to skew color on outdoor film.
NOTE: Light temperature should not be confused with illumination. A 75-watt incandescent bulb has a light temperature of 2850 but hardly emits enough illumination for a quality photograph.
Of course, most people who pick up a camera now don't worry about film as they are using digital products that have auto-white balance settings. Given the abundance of digital cameras and white-balance settings, is light temperature still a factor to consider? Absolutely! Auto-white balance settings are rarely, if ever, accurate enough for professional work, especially if one places any type filter on the front of the lens. Even pre-loaded settings such as "shade" or "overcast" are not likely to be as reliable as professional work demands.
For example, a "shade" setting of 7000K might be appropriate for light shade in summer, but in heavy shade would result in a definite chromatic shift toward green and yellow.
Digital photographers generally have two options. One is to set a custom white-balance by taking a reference picture of a white card in the given light setting. This works in situations where the light source remains at a constant temperature. However, the reference photo quickly becomes obsolete when shooting outdoors. More appropriate may be setting the color temperature manually. Most Canon EOS DSLR and Nikon D series cameras have a manual range from 2300K to 10,000K, which pretty much covers all but the hottest of summer skylights.
However, such settings are useless if the person holding the camera doesn't know how to properly apply them!
In addition to the scale above, some temperature settings worth remembering are:
Granted, software tools such as Photoshop provide the digital photographer with multiple tools for correcting color issues caused by an incorrect white balance. However, relying on software is inefficient when faced with more than two or three images. Attempting to resolve white balance issues through batch processing delivers nothing short of mediocrity. A wise photographer solves light temperature issues on the camera, either through film choice or by adjusting digital light temperature settings.
Try it. The difference in the quality of one's photography grows the more one understands the elements going into a great picture.
The most basic, elemental form of energy, light is the most critical element for all forms of life. As photographers, we wrestle constantly with light, whether there is too little, too much, or coming from the wrong direction. Much of the anxiety can be eased by putting more effort to understanding this most fundamental element and its most critical role in creating the pictures we love.
Visible light, what the human eye is capable of seeing, is but a very small part of the eletromagnetic spectrum. The combined fluctuations of electric and magnetic waves transport energy from point A to point B. As light interacts with matter, the wave changes, allowing the human eye to assess the qualities of the matter. These changes in light are what our eyes interpret as color.
We measure light, and subsequently color, in terms of temperature. Without getting bogged down into scientific explanations, the amount of heat emitted from a light source determines its color (with the exception of fluorescent bulbs). These temperatures, measured most typically on what is called a black-body scale, are important in helping us determine what it absolute white. When shooting film, for example, tungsten film recognizes white according to the temperature of light emitted from a tungsten bulb, which is 2800 K. Daylight film, by contrast, recognizes pure white on a range between 5500-6000 K. Using film inappropriate to the light source inevitably alters how the film interprets color. Fluorescent light presents a challenge to photography because the light does not originate with a heat source and therefore varies in temperature, making it nearly impossible to find an accurate point for white balance.
What difference does any of this make?
Consider the challenges of outdoor photography. Experienced photographers will often talk about catching the "magic hour," within one hour after sunrise or one hour before sunset. The reason is because of the temperature of sunlight during those periods of time.
Look at the following outdoor temperature scale:
| Sunlight: Sunrise or Sunset | 2000 |
| Sunlight: One hour after Sunrise | 3500 |
| Sunlight: Early morning or late afternoon | 4300 |
| AverageSummer Sunlight at Noon (mid-latitudes) | 5400 |
| Direct Mid-Summer sunlight | 5800 |
| Overcast | 6000 |
| Daylight Fluorescent Lamp (see note) | 6300 |
| Average summer sunlight | 6500 |
| Light summer shade | 7100 |
| Average summer shade | 8000 |
| Summer skylight | 9500 - 30,000 |
NOTE: There are six different types of fluorescent lamps, making it virtually impossible to know what the exact white temperature is going to be. Even the best fluorescent filters tend to leave a greenish hue, making fluorescent light a challenge for photography.
If we assume that the professional tungsten lamp temperature of 3200 K is ideal for portrait photography, then once the sunlight temperature exceeds 3500 K, one can anticipate increasingly severe problems as the light temperature steadily climbs. Even overcast skies emit a temperature hot enough to skew color on outdoor film.
NOTE: Light temperature should not be confused with illumination. A 75-watt incandescent bulb has a light temperature of 2850 but hardly emits enough illumination for a quality photograph.
Of course, most people who pick up a camera now don't worry about film as they are using digital products that have auto-white balance settings. Given the abundance of digital cameras and white-balance settings, is light temperature still a factor to consider? Absolutely! Auto-white balance settings are rarely, if ever, accurate enough for professional work, especially if one places any type filter on the front of the lens. Even pre-loaded settings such as "shade" or "overcast" are not likely to be as reliable as professional work demands.
For example, a "shade" setting of 7000K might be appropriate for light shade in summer, but in heavy shade would result in a definite chromatic shift toward green and yellow.
Digital photographers generally have two options. One is to set a custom white-balance by taking a reference picture of a white card in the given light setting. This works in situations where the light source remains at a constant temperature. However, the reference photo quickly becomes obsolete when shooting outdoors. More appropriate may be setting the color temperature manually. Most Canon EOS DSLR and Nikon D series cameras have a manual range from 2300K to 10,000K, which pretty much covers all but the hottest of summer skylights.
However, such settings are useless if the person holding the camera doesn't know how to properly apply them!
In addition to the scale above, some temperature settings worth remembering are:
| Match flame | 1700 |
| Candle flame | 1850 |
| Full Moonlight | 4100 |
| Electronic Flash | 5500-6000 |
| Xenon arc lamp | 6420 |
| TV Screen | 9300 |
Granted, software tools such as Photoshop provide the digital photographer with multiple tools for correcting color issues caused by an incorrect white balance. However, relying on software is inefficient when faced with more than two or three images. Attempting to resolve white balance issues through batch processing delivers nothing short of mediocrity. A wise photographer solves light temperature issues on the camera, either through film choice or by adjusting digital light temperature settings.
Try it. The difference in the quality of one's photography grows the more one understands the elements going into a great picture.
Labels: color, light, photography, temperature, white balance
posted by Charles at
9:14 PM
