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Lighting curation site

Lighting terminology site

Lighting is an essential element in our lives and activities, and plays a role in improving the atmosphere and functionality of a space. In recent years, lighting technology has constantly evolved through the fusion of science and design, providing innovative technologies to make our lives more comfortable and effective.

There are many technical terms and concepts in the world of lighting. For example, the type and characteristics of light sources, the distribution and diffusion of light, color temperature, and light quantity. Understanding these terms and concepts is essential for lighting planning, lighting design, and the selection of lighting equipment.

This site explains basic terms and concepts related to lighting. This will help you deepen your knowledge of lighting and create a better lighting environment.

Lighting fixtures are not just for lighting, but are powerful tools for creating a space, improving its functionality, and even improving the quality of our lives. We hope that through lighting terms, we can deepen your knowledge and understanding of lighting and help you realize a better lighting environment.

Lighting Terminology

Regarding lighting terminology, we will mainly explain terms that are necessary when proceeding with meetings and lighting plans. In particular, rather than judging based on the brightness (number of lumens) alone, we would like you to keep the following terms in mind when proceeding with lighting plans and meetings as you imagine what kind of light distribution and appearance will create a balance of brightness while imagining where the atmosphere will be centered.

About the terminology of light

In incandescent and fluorescent lamps, light intensity was measured in watts (W), but with the change to LED light sources, light intensity is measured in lumens (lm). Also, the JIS standard uses lux (lx) as the standard for illuminance, but in recent years, there has been a trend to emphasize candela (cd) as a guideline, as the sense of brightness is also given importance.

※ Reference diagram: © 2021 Shikakushika Quote

Typical terms include:

  • Luminous flux (lumens: lm) - A unit that indicates the amount of light emitted from a light source.
  • Luminous intensity (candela: cd) - A unit that indicates the intensity of light emitted from a light source in a specific direction.
  • Illuminance (lux: lx) - Indicates how much light emitted from a light source reaches a certain surface or area. The illuminance standard table in the JIS standard and the Illuminating Engineering Institute of Japan is mainly used as a guide to brightness.
  • Luminance (candela per square meter: cd/m2) - A unit used to evaluate the brightness of the light emitted or reflected by an object itself. It is the amount of light energy emitted or reflected per unit area.

Other terms include:

  • Average color rendering index (color rendering: Ra) - A standard value for whether the color of an object appears faithful to natural light when illuminated by a light source.
  • Glare (candela per square meter: cd/m2) This refers to the brightness of light or the glare caused by reflection. Glare can cause eye fatigue and visual impairment, which can lead to reduced work efficiency.
  • Light distribution This refers not only to the spread of light, but also to the intensity of light and the direction in which it is emitted. A light distribution curve is a curve that expresses the intensity of light and its direction.
  • Uniformity This is an index of how evenly lighting is distributed within a space. In general, a uniformity factor between 1.0 and 0.5 at minimum and maximum illuminance is considered ideal.
  • Maintenance rate This is a predicted value of the rate at which the initial average illuminance in a facility will decrease over time. The value will vary depending on the environment in which the lighting fixture is used. Standard values ​​are listed in lighting documents from the Illuminating Engineering Institute of Japan, Toshiba, Panasonic, etc.
  • Illuminance measurement surface For desks and work surfaces, it is floor surface + 80cm ± 5cm. In the case of Japanese-style rooms, it is + 40cm ± 5cm above tatami mats. In corridors and outdoors, it is floor surface/ground surface + 15cm or less. * Generally, the measurement surface is 0.0cm. There are also measurement surfaces that differ depending on the type of business, such as floor surface + 120cm for beauty salons and floor surface + 100cm for play areas, with measurement surfaces that place emphasis on the work surface.

As for the terminology, most of it is used in meetings, etc., but there is a tendency for luminance (perception of brightness) to become more important in the future.

Color temperature (light color)

Color temperature is an element of light necessary to create a warm or refreshing atmosphere in a space. In recent years, with the shift to LED light sources, lighting manufacturers are promoting dimming systems that adjust the brightness and color temperature of light to regulate the circadian rhythm, which is based on basic functions such as human body temperature and hormone secretion, in order to regulate the rhythm of approximately 24 hours.

※ Reference image: colorplettes.jp

It indicates the "color" of the light spectrum distribution based on the characteristics of the color emitted by the light source or light. The higher the color temperature of the light, the closer it is to bluish white or blue, and the lower the color temperature, the closer it is to reddish white or yellow. Color temperature is expressed in units of Kelvin (K). In addition, to check the color temperature, you can check the wavelength ratio of light by using a spectral distribution chart, which continuously shows the amount of light wavelength components.

  • Spectral distribution (nanometers: nm)　The "spectral distribution" is a graph showing the ratio of light by wavelength. The color temperature is determined by the ratio of the spectral distribution. The spectral distribution can be expressed in the range of 4000~700 (380~780) nm, where the eye is most sensitive. The graph shows the components of the light from the light source, such as what wavelengths of light are included and their intensity.

For example, in the case of everyday natural light, the wavelengths are almost evenly distributed in the range of 400~700 (380~780) nm.

In the case of incandescent lamps, the light emission principle is due to heat generation, which results in a natural curve. In the case of LEDs, the light emission principle differs depending on the device light source. As a result, the spectral distribution ratio also has an extreme curve. In recent years, LEDs with a spectral distribution close to natural light due to their high color rendering properties have become popular.

*Each diagram is taken from the CCS Inc. website, "Characteristics of Natural Light LEDs ① Reproducing Sunlight"

*For more information on the principles of LED light emission, please refer to "LED Basics" on the Panasonic Corporation website.　　　　　　*Click here to read "LED Basics"

Types of lighting fixtures

When selecting lighting fixtures, it is important to consider five factors.

① Use and characteristics of the space: Select lighting fixtures with the appropriate brightness and color temperature for the purpose.

② Design and style: Select lighting fixtures that harmonize with the style and design of the room.

③ Effective placement: Consider what type of lighting is needed in which location in the room, and place it at the appropriate height and position.

④ Energy efficiency and durability: LED fixtures are generally economical and environmentally friendly products, but the power supply and lighting materials used in LED fixtures must also be taken into consideration.

⑤ Budget: Lighting fixtures vary greatly in price, so it is important to select fixtures that take into account the required functions and design within your budget.

※ Reference diagram: © 2021 Shikakushika

Typical lighting fixtures include:

  • Pendant light: A lighting fixture that hangs from the ceiling to provide light for your hands. Note that you need to consider the installation height for proper brightness and the installation interval when using multiple lights.
  • Ceiling light: Mainly used to brighten the entire room. Please refer to the lighting fixture catalog for sizes for 6 tatami mats, 8 tatami mats, etc.
  • Floor stand: A lighting fixture that stands on the floor and is used as indirect lighting or reading light.
  • Table light: A lighting fixture that is installed on a desk or table and is used for visual work.
  • Bracket light: A lighting fixture that is installed on a wall and is used for indirect lighting and accent lighting.
  • Downlight: A lighting fixture that is mainly installed on the ceiling by recessing or directly attaching it, and shines light downward. It is mainly used when you want to use different light spreads such as wide angle, medium angle, and narrow angle.
  • Spotlight: A lighting fixture that is mainly installed on a wiring duct, ceiling, or wall, and the direction of the light can be freely changed. Mainly used when you want to use it in places or objects where you want to attract attention with the spread of light, such as wide angle, medium angle, or narrow angle.
  • Universal downlight: A downlight with spotlight functionality. The direction of the light can be freely changed, and it is mainly used when you want to use it in places or objects where you want to attract attention with the spread of light, such as wide angle, medium angle, or narrow angle.
  • Chandelier: Equipped with many lamps, it is suitable for ensuring sufficient brightness even in large rooms or spaces with high ceilings. A major feature is that it creates an impression of space with a luxurious and decorative design fixture.

Other types include indirect lighting, under-shelf lighting, and footlights.

We will gradually add more in the future.

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