What Is a Light Meter?
A light meter is a device that numerically measures color using Kelvin (K) as an index for the distribution of wavelengths of light emitted by an object.
Developed in the field of photography, light meters are classified as photographic exposure meters, lighting exposure meters, and other.
Related devices include color luminance meters, which simultaneously measure the luminance of light and the correlated color temperature based on the relationship between the physical properties of color and human perception, and color illuminance meters, which can measure illuminance, which indicates the brightness of irradiated light, RGB chromaticity, and color difference, which is the distance in color space.
Uses of Light Meters
Light meters have a variety of applications in photography, lighting, and digital screens.
They can be used to measure the color temperature of different light sources in photography, for example, sunlight at 5500 K and tungsten light at 3200 K. This information can be used as an index for correction during photography, output, and printing.
Similarly, light meters for lighting can be used to physically measure the color of artificial light sources to help reproduce the natural, inherent colors in sunlight.
It is also applied to white balance and color adjustment in the digital domain.
Principle of Light Meters
Among color thermometers, photographic exposure meters measure color temperature based on two colors (red and blue) from spectral data of multiple wavelengths.
The color temperature can also be measured by the amount of color temperature compensation using a filter on the light source, which uses LB (color temperature conversion) mired (microreciprocal degree) values based on the inverse of the color temperature, CC (Color Compensating) density values, etc.
The LB value is based on the fact that the photographic film will appear redder at lower color temperature settings and bluer at higher color temperatures.
The CC density value is measured from the value required to correct the three primary colors cyan, magenta, and yellow and their complementary colors red, green, and blue for natural color.
A light meter for lighting, also called a color illuminance meter, measures the correlated color temperature, which is the temperature of blackbody radiation that appears to approximate the color of the light source, based on spectral sensitivity as perceived by the human senses.
It is necessary to understand the characteristics of the exposure meter depending on the device, such as the fact that the correlated color temperature cannot represent the color green, and whether it is compatible with LEDs or not, depending on the purpose.