Principles of Illumination PDF

PRINCIPLES OF ILLUMINATION Prepared By: Engr. Christopher S. Dolino, MoE  Definition of Terms ILLUMINATION Is define as the intensity of light per unit area. ELECTRIC ILLUMINATION Is the production of light by means of electricity and its application to provide efficien...

PRINCIPLES OF ILLUMINATION Prepared By: Engr. Christopher S. Dolino, MoE  Definition of Terms ILLUMINATION Is define as the intensity of light per unit area. ELECTRIC ILLUMINATION Is the production of light by means of electricity and its application to provide efficient, comfortable and safe vision.  Lighting Design Quantity of Light Refers to the amount of illumination or luminous flux per unit area. Quality of Light Refers to the distribution of brightness in the lighting installation.  Factors that affect Illumination Brightness is the light that seems to radiate from an the object being viewed. Contrast Is the difference in brightness or the brightness ratio between an object and its background. Glare Is a strong, steady, dazzling light or reflection. Diffuseness Refers to the control of shadows cast by light.  ESTIMATING ILLUMINATION AND BRIGHTNESS  Illuminance Meter Available The comparator Type Requires the operator to make a brightness equivalence judgment between the target and background. The Direct Reading Type Is basically an illumination meter equipped with a hooded cell arranged to block oblique light. Accurate Laboratory Instrument Is unsuitable for fieldwork.  Units of Illumination Footcandle (fc) Is the amount of light flux density. It is the unit of measure used when describing the amount of light in a room and is expressed in lumens per square foot. Footlambert (fl) Is defined as the luminance of a surface reflecting, transmitting or emitting one lumen (lm) of illumination per square foot of area in the direction being viewed or the conventional unit of brightness or luminance. Formula:  ILLUSTRATION 1 A 40-watt fluorescent lamp 120 centimeters (48 in.) long produces 3,200 lumens of light in a room having a general dimensions of 10 x 20 ft. Find the illumination on the floor. Solution:  Points to Remember “In the absence of footcandle table of equivalent for a particular fixture, a rule of thumb of 10-30-50 illumination level is applied.” 10 – footcandle is adequate for halls and corridors. 30 - foodcandle is sufficient for areas between work stations such as in offices other than desk areas. 50 – footcandle is satisfactory on spaces where office work is being done.  ILLUSTRATION 2 From illustration 1, Find the luminance if the reflectance factor of the wall is 40%. Solution: Footlambert = Footcandle x Reflectance factor = 16 fc x 40% = 6.4  Lighting Units in Metric Measures Note: Lumens flux remains in Lumens; but Illumination or light flux is expressed in Lux. Thus Table 1: Approximate Reflectance Factor  Table 2: Table of Comparison Millilambert – is more conveniently used than the lambert because the value of lambert is greater than what usually encountered.  ILLUSTRATION 3 A 40 watts x 120 centimeters long fluorescent lamp produces 3, 2000 lumens of light in a room having a general dimension of 10ft. X 20ft. Compute the illumination on the floor comparing the English and the Metric units. Solution by COMPARISON Another Solution  ILLUSTRATION 4 Compute the brightness of a fixture with a 1’ x 4’ plastic diffuser having a transmittance of 0.6 and illuminated by 2 pcs. 3, 200 lumen lamp assuming 100% use of light flux. Solution:  ILLUSTRATION 4 Compute the brightness of a fixture with a 1’ x 4’ plastic diffuser having a transmittance of 0.6 and illuminated by 2 pcs. 3, 200 lumen lamp assuming 100% use of light flux. Solution:  Coefficient of Utilization and Maintenance Factor Coefficient of Utilization (cu) - is a measure of the efficiency of a luminaire in transferring luminous energy to the working plane in a particular area. Maintenance Factor (mf) - The ratio of illumination on a given area after a period of time to the initial illumination on the same area; used in lighting calculations to account for the depreciation of lamps or reflective surfaces (or the like). Usable Initial footcandle – is equal to the footcandle produced by the coefficient of utilization (cu) Table 3: Coefficient of Utilization  ILLUSTRATION 5 A school classroom with general dimension of 24 x 30 feet is lighted with 10 fluorescent lamp 4F 40 T12 WW rapid start lamp. Calculate the initial and maintained illumination in foot candle (English) and Lux (Metric), assuming that the coefficient of utilization (cu), is 0.35 and the maintenance factor (mf) is 0.70.  Solution 1 (English Measure) Lamp lumens = 10 fixtures x 4 lamps per fixtures = 40 x 3,200 lumens per lamp = 128,000 lumens Initial Foot Candle = Lumens x cu x mf Area  Solution 2 (By the Metric Measure SI) Convert feet to meter : 24 ft. = 7.32 m. 30 ft. = 9.14 m.  ILLUSTRATION 6 An office room with general dimension of 8 x 20 meters is to be lighted at an average maintained foot candle of 50. How many 3-lamp fixtures of 120 centimeters long F40 T12 WW rapid start fluorescent lamps are required assuming 0.38 cu and 0.75 mf? Solution: ILLUSTRATION 6 Table 6: Efficacy of various lamps  ILLUSTRATION 7 An entire office floor is lighted at an average maintained 538 lux or 50 fc. The floor measures 20 meters by 50 meters and is divided into bays measuring 4 m x 5 m. Using 2-lamp of F40 T12 CW rapid start preheat lamp, find the number of fixtures required. Assume an economy grade fixture with a low cu of 0.35 and mf of 0.70.  Solution 1 1. Solve for the number of fixtures per bay, Refer to table 7. for F40 T12 CW, Lumens = 3, 150 2. Solution 2 Figure 1: Distribution of Lights per Bay Fluorescent Lamp Data Fluorescent Lamp Data Thank You!