Principle of lumination design
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The document discusses principles of illumination design, including definitions of key terms like luminous flux, solid angle, luminous intensity, and color temperature. It covers factors that affect visual tasks like size, luminance, contrast and glare. Basic definitions are provided for concepts such as candela, utilization factor, depreciation factor, candlepower, and mean horizontal candlepower. The document also discusses the light spectrum, types of lighting (natural vs artificial), light sources, luminous efficiency, and color rendering.
Principle of lumination design
- 1. Principles of Illumination Design: • Basic Definations • Visual task is the term given to an activity requiring visual perception and located in a certain place. Factors affecting Visual Task 1. Size: Making objects larger, or moving them closer to our eyes, makes them easier to see. We need less light to perform a task when detail size is increased. 2. Luminance: Visual performance requires sufficient light. The optimum level of luminance needed to perform a task depends on the nature of the activity, e.g. -- using a keyboard or reading newsprint. 3. Contrast: Luminance variation, or contrast, allows us to distinguish a visual task from its surroundings. As shown in the example, greater contrast between letters and their background improves readability. 4. Glare: Bright light which interferes with visual perception is called glare. An overly bright area in our field of vision reduces our ability to perceive visual information needed for task performance
- 2. Basic Definations • Luminous flux is the measure of brightness of a light source in terms of energy being emitted. Luminous flux, in SI units, is measured in the lumen (lm). • Solid angle: The solid angle has defined an angle Which is subtended at a point in space by an area
- 3. Basic Definations • Luminous intensity, the quantity of visible light that is emitted in unit time per unit solid angle. • Candela (cd), unit of luminous intensity in the International System of Units (SI), defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and has a radiant intensity in that same direction of 1/683 watt per steradian (unit solid angle). • Utilization factor: Utilization Factor or Co-efficient of utilization. It may be defined as “the ratio of total lumens received on the working plane to the total lumens emitted by the light source” • Utilization factor =Lumens received on the working plane/Lumens emitted by the lamp • Depreciation or Maintenance factor: the ratio of illumination under normal working condition to the illumination when everything is clean or new.
- 4. Basic Definations • Candlepower (abbreviated as cp or CP) is an obsolete unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents. • MHCP: It is known as the mean of candle power in all directions in the horizontal plane containing the source of light.
- 6. There are two types of lighting • 1. Natural Lighting • 2. Artificial Lighting
- 7. • Artificial light can be created by combining red (R), green (G) and blue (B) components Changes in the RGB ratios change the characteristics of the light and therefore the mixture ratios of RGB • fluorescent substances is an important point to be taken into consideration when creating artificial lights
- 8. Artificial lights sources, • First generation – bulbs based on heating of a wire filament • Second Generation – Gas discharge lamps (Neon lights) • Third generation – Light- Emitting Diode (LED) lamps
- 9. Luminous efficiency • Light sources convert electrical power into visible radiation (light). However, the major part of electrical power consumed by a light source is converted into heat. • For example, incandescent lamps only emit 5% of their electrical power as light and fluorescent lamps between 20% and 40%.
- 10. Color Temperature • The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source. • Color temperature is a measurement used to describe the relative color of white light. • Colour temperature refers to the appearance of light provided by a light bulb. • Colour temperature is expressed in Kelvins and measured on a numbered scale. • Color temperatures over 5000 K are called "cool colors" (bluish), while lower color temperatures (2700–3000 K) are called "warm colors" (yellowish)
- 11. Colour Rendering. • Describes how a light source makes the color of an object appear to human eyes. • Color rendering, expressed as a rating from 0 to 100 on the Color Rendering Index (CRI). • Color rendering describes how well the light renders colors in objects.