Basic quantities in lighting help us to specify light and its characteristics accurately and in terms of standard units. In lighting, there are various concepts that are used to measure and understand the characteristics of light and light sources. Below, I explain the basic quantities in lighting:
What is light?
Light is one of the electromagnetic rays that form part of the electromagnetic spectrum. Light exists as an electromagnetic wave in nature and reaches us in the form of light rays from light sources such as the sun, lights, or other light sources.
Light is in the electromagnetic spectrum between infrared and ultraviolet . Light waves can have different wavelengths, and this difference in wavelength changes the color of light as well as its different characteristics. Visually, waves with shorter wavelengths are commonly referred to as infrared or ultraviolet light. Waves with longer wavelengths are known as blue or infrared light.
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Light is one of the basic factors in our vision and is composed of photons (light particles) that have the ability to radiate and absorb. When photons hit our eyes, they cause electrical signals in the retina that are transmitted to the brain and eventually form the image we see. In short, light is one of the most important elements in our lives, causing visual phenomena, lighting, and many other sensory experiences.
What are the basic quantities in lighting?
Now we introduce the most important quantities related to lighting.
Luminous Flux
Lumen is a unit of measurement of the brightness of a light source, which is defined based on the sensitivity of the human eye to light. In other words, lumen indicates the amount of light received by the human eye. Luminous flux is represented by the symbol Φ and is measured in lumens (abbreviated as lm) and expresses the amount of light emitted from a source in all directions.
Illuminance
Lux represents the light intensity of a light source on a specific surface (usually the ground or another horizontal surface). More precisely, lux indicates the light output of one lumen per square meter on a certain surface. This quantity expresses the amount of light available at a certain point of space or surface. The intensity of light is represented by the symbol E, and the unit of measurement of light intensity is lux (Lux), and it is measured with a device called a lux meter.
Luminous Intensity
Candela is a unit of measurement of light intensity of a light source in a specific direction. Candela represents the amount of light that a light source emits in a specific direction. This quantity is specific to targeted light sources such as flashes and adjustable directional lights. Light intensity is denoted by the symbol I and this quantity is displayed by the light intensity distribution curve or LDC.
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What is the light intensity curve?
The Light Intensity Distribution Curve represents the spatial distribution of the light intensity of a light source in a specific plane or space. This curve shows how the light intensity changes from the light source to its surroundings and shows the points that have more or less light intensity.
The light intensity distribution curve is usually displayed as circles, rectangles or curves in the diagram. The light intensity is determined for different horizontal and vertical angles from the light source, and this curve shows in which directions the light from the source is stronger or weaker.
Luminous Efficiency:
Light efficiency indicates the efficiency of a light source, which is how much of the electrical energy we give to a lamp or light source is returned to us in the form of light. In other words, the optical gain shows how much light is actually thrown into the environment in proportion to its energy consumption. In simpler terms, the ratio of luminous flux to the electrical power consumed by the lamp is called the light efficiency of the lamp. The unit of light output is lumens per watt (lm/w), which actually shows how much light it produces with each watt.
Color Rendering Index:
It indicates the ability of a light source to correctly reproduce colors. This index ranges from 0 to 100, and if it is close to 100, the light source has the best ability to reproduce colors. This index is important because it shows how much more realistic and accurate colors are perceived by others. The closer this number is to 100, it means that objects under this light are closer to their true color and can be seen better.
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Color Temperature:
Color temperature represents the color spectrum that a light source emits. This temperature is measured in Kelvin. Light sources with a higher color temperature generally have a cooler, bluer light, while light sources with a lower color temperature have a warmer, more yellow light. Color temperature is one of the important factors in choosing the right light for different environments and can have an important effect on the visual experience and emotions related to spaces and images.
For example, in home environments and rest rooms, warmer colors are usually used to create a feeling of relaxation and comfort. While in work environments, some designs and images are better coordinated with cold lights to add more focus and energy to working or watching scenes.
Luminance
Luminance refers to the amount of light emitted by a surface, an object or an area in space; or the light that is reflected from the light source towards that surface or object. This visual feature refers to the brightness and vision of a point or surface.
Luminance is measured in candela units in square meters or nits (cd/m²). The brightness of an object depends on many factors. including the type of light source, the property of the surface of the object, the angle of light projection, the effect of the lighting of the surrounding environment and the type of sensor or eye that receives the light. Hence, luminance can affect the effect of reality in general and in particular in realistic 3D environments and VR experiences. One of the important and common features in lighting, visual arts, light physics and many other fields is luminance.
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Glare
Glare is an important term in lighting and visual science that refers to problems caused by bright lights or strong rays relative to an image or observer. This phenomenon often causes a decrease in clarity, darkness, contrasts and visual changes due to the difference in light intensity in a scene. Glare may be directly facing a light source or from reflective surfaces such as glass, water, snow, or some lamp surfaces. Some of the causes and factors that cause glare are:
- Light intensity difference: The presence of very bright lights or strong light sources in a scene can cause a sharp difference in the intensity of the ambient light and cause glare.
- Light reflection from reflective surfaces: Glass, water, snow, or lamp surfaces that reflect light back into the observer’s view can exacerbate glare.
- Disturbing lights: Lights that shine directly and without reflection from the source may reduce the clarity and comfort of the observer’s vision.
- Damage to sensitive surfaces: Glare can lead to damage to sensitive surfaces such as the eyes, especially in front of very bright lights such as sunlight or strong lamps.
In order to reduce glare and improve visibility and clarity of images, suitable lighting methods and measures are used, such as the use of glare filters, appropriate location of light sources, and light intensity control. Also, in the design of indoor and outdoor environments, it is important to consider the proper direction and position of lights in order to reduce the possibility of glare. if you need lighting products see chique lighting online shop.
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