The spectral quality of light used to create an image is a factor of filter spectral characteristics, illumination color temperature and subject reflectance.
The spectral characteristics of the lighting will effect spectral selectivity imaging efforts.
The following tables provide color temperature values for some common light sources.
Color temperature is specified as degrees Kelvin and in MK-1 values (see table below for common conversion factors).
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Light Source Color Temperatures
| DAYLIGHT COLOR TEMPERATURES | ||
| Description | Degrees Kelvin | MK-1 Values |
| Clear Blue Sky | ||
| Rainy, Misty Daylight | ||
| Overcast Daylight | ||
| Direct Sun + Clear Blue Sky | ||
| Summer Sunlight (9am to 3pm) | ||
| Summer Sunlight (before 9am or after 3pm) | ||
| Electronic Flash (Typical) | ||
| ARC LAMP COLOR TEMPERATURES | ||
| Description | Degrees Kelvin | MK-1 Values |
| Xenon Arc (unfiltered) | ||
| White Flame Carbon Arc | ||
| Yellow Flame Carbon Arc | ||
| FLUORESCENT LAMP COLOR TEMPERATURES (Approximate) | ||
| Description | Degrees Kelvin | MK-1 Values |
| 'True Daylight' Color Match Tubes | ||
| 'Daylight' Cool White Tubes | ||
| 'Warm White' Tubes | ||
| TUNGSTEN COLOR TEMPERATURES (Approximate) | ||
| Description | Degrees Kelvin | MK-1 Values |
| Photoflood & 3400K Tungsten-Halogen | ||
| Tungsten-Halogen and Photolamps | ||
| Projection Lamps (500 to 1000 Watts) | ||
| General Purpose Lamps (200 to 500 Watts) | ||
| Household Lamps (100 to 150 Watts) | ||
| Household Lamps (60 Watts) | ||
| Household Lamps (40 Watts) | ||
| Daylight and tungsten illumination will produce different spectral sensitivity plots on panchromatic film. The following illustration shows the tungsten and daylight spectral sensitivity plots for a typical panchromatic emulsion. |
| The spectral energy plots for tungsten and sunlight illumination are also different. Tungsten illumination is much "warmer" and contains much more energy in the red portion of the spectrum. Sunlight has more energy in the "cooler" or blue portion of the spectrum. The following illustration shows spectral energy plots for sunlight and two types of tungsten illumination. |
| The color temperature of tungsten lamps varies with line voltage. The following table shows how the color temperature of a 3200 degree Kelvin lamp varies with changes in line voltage. |
| Water acts like a blue pass band filter. The following illustration shows the absorption density curve for sunlight entering water (depth in feet and meters). |
| CANDLE COLOR TEMPERATURES (for Reference) | ||
| Description | Degrees Kelvin | MK-1 Values |
| Standard Candle | ||
| Candle Flame | ||
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Color Temperature Conversion Factors - The following list provides color temperature conversion factor equations.
MK |
| Value: | Equation: |
| Mired | = MK-1 |
| Decamired | = mired / 10 |
| Decamired | = 100,000 / Kelvin |
| Mired | = 10 * decamired |
| Mired | = 1,000,000 / Kelvin |
| Kelvin | = 100,000 / decamired |
| Kelvin | = 1,000,000 / mired |
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