Difference Between Light Source and Illuminant

Light Source vs Illuminant
 

Light sources and illuminants are very important concepts in fields of physics, photography, astronomy and many other sciences. Illuminants and light sources are commonly mistaken for the same concept even though they are a bit different from each other. A good understanding in light sources and illuminants is required in order to excel in fields that rely heavily on these concepts. In this article, we are going to discuss what light sources and illuminants are, their definitions and applications, similarities between light sources and illuminants, and finally the difference between light sources and illuminants.

Light Source

There are several types of light sources we encounter in our daily lives. The most common type of light source we encounter is the thermal light sources. A thermal light source creates light from the excitation and relaxation of electron inside atoms and the thermal oscillation of electrons. Any object having a temperature above the absolute zero emits electromagnetic waves. For black bodies, it must be noted that the object will emit the whole electromagnetic spectrum but with different intensities in each region. The wavelength in which the highest number of electrons are emitted can be calculated using the Wien’s displacement law. This law can be identified with the following equation. λmT = constant where λmis the wavelength in which the maximum number of photons are emitted. The constant used here is the Wien’s constant and the temperature must be applied in the form of kelvin. A light source is something that actually creates light. Apart from thermal light sources, LASERs, fluorescent bulbs, semiconductor diodes are also used as light sources. Light sources are largely used in photography. In photography, the light sources are mainly the sun, flashlights, ambient light and spotlights.

Illuminants

Illuminants are a special class of lighting methods. There are several kinds of standard illuminants. The class-A of standard illuminants refers to domestic filament lights. The class-B and C refers to daylight sources. These are obtained by filtering A-class illuminants. The class-D refers to the natural daylight. These were developed after class-B and C; therefore, they are more accurate and advanced than the class-B and class-C illuminants. The class-E refers to a full visible spectrum emission with equal photons in each wavelength. The class F illuminants refer to the standard fluorescent light spectrum. These standard illuminants are very important in fields such as photography. The class of the artificial lights used to create the lighting can directly impact the photograph and the post processing.

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