Short term interior design courses in chennai - Aleesha Institute
During the past several decades, most lighting designers
have been using the so-called "lumen method" to design
illumination systems for interior space. For a design which
yields average illumination, the coefficient of utilization (CU)
is the one single most useful factor. However, this design
method will only provide a mediocre lighting environment and
most likely result in wasted energy. During the last decade,
rapid changes were taking place in lighting design techniques.
As people become more energy conscious and better understand human visual performance, lighting designers find the
conventional techniques are becoming less and less satisfactory, essentially because the lumen method procedure lacks
two desirable characteristics.
1) Light should be placed specifically on the task where it is
most needed, while reducing the illumination level in the
surrounding areas. Failure to do so often results in a
waste of energy.
2) The lumen method does not allow the designer to
increase the visual effectiveness of his lighting by
optimizing available candlepower.
This clearly indicates the need for the use of improved new
design concepts.
NEW METHOD OF DETERMINING LIGHTING LEVELS Among the many new concepts for lighting design, the first one to be discussed is the new method of determining lighting levels which was formally introduced in [9]. In the past, when Paper IUSD 83-35, approved by the Production and Application of Light Committee of the IEEE Industry Applications Society for presentation at the 1983 Industry Applications Annual Meeting, Mexico City, Mexico, October 3-7. Manuscript released for publication January 5, 1984. The author is with North American Philips Lighting Corporation, 1 Westinghouse Plaza, Bloomfield, NJ 07003. TABLE I ILLUMINANCE CATEGORIES FOR SELECTED TASKS Functional area and task description Assembly Simple Moderately difficult Difficult Very difficult Exacting Machine Shops Rough bench, machine work Medium buffing, grinding Extra-fine machine work Off ices General offices Reading poor reproductions Reading ink handwriting Reading high-contrast print Draf+tirg rooms Detailed drafting Rough layout drafting Service Areas Stairways, landings, doorways Lobbies Toilet rooms I llu minance category D E F G H D E H F D D F E C C C Source: A comprehensive table given in the sixth edition of the IES Lighting Handbook. lighting designers wanted to know the recommended illuminance for a given task, they would look in the IES Lighting Handbook to find a recommended level and then design an illumination system for the task using the recommended level as a minimum. This procedure provides very little latitude for fine-tuning lighting design. The new method for determining required illuminance provides three categories based on the room function and visual task available to the designers. They are 1) rooms involving visual tasks for which there are tables of prescribed illuminance; 2) rooms involving-visual tasks for which there are tables of measured visibility, or for which visibility can be measured; 3) rooms not involving visual tasks. In each case, a more comprehensive investigation of required illuminance is performed according to the following steps. a) Instead of a single recommended illuminance value, a category letter is assigned (Table I). b) The category letter is used to define a range of illuminance (Table II). c) From within the recommended range of illuminance, a specific value of illuminance is selected after consideration is given to the average age of workers, the importance of speed and accuracy, and the reflectance of task background. The importance of acknowledging the speed and accuracy with which a task must be performed is readily recognized. Less obvious is the need to consider the age of workers and the reflectanee of task background. To compensate for reduced visual acuity, more illuminance is needed. Using the average age of workers as the age criterion is a compromise between the need of the younger and the older workers and, therefore, a valid criterion. Task background affects the ability to see because it affects contrast, an important aspect of visibility. More illuminance is required to enhance the visibility of tasks with poor contrast. Reflectance is calculated by dividing the reflected value by the incident value. The data- given in Tables Ill and IV are taken from the IES handbook and are applied to provide a single value of illuminance from within the recommended range.
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NEW METHOD OF DETERMINING LIGHTING LEVELS Among the many new concepts for lighting design, the first one to be discussed is the new method of determining lighting levels which was formally introduced in [9]. In the past, when Paper IUSD 83-35, approved by the Production and Application of Light Committee of the IEEE Industry Applications Society for presentation at the 1983 Industry Applications Annual Meeting, Mexico City, Mexico, October 3-7. Manuscript released for publication January 5, 1984. The author is with North American Philips Lighting Corporation, 1 Westinghouse Plaza, Bloomfield, NJ 07003. TABLE I ILLUMINANCE CATEGORIES FOR SELECTED TASKS Functional area and task description Assembly Simple Moderately difficult Difficult Very difficult Exacting Machine Shops Rough bench, machine work Medium buffing, grinding Extra-fine machine work Off ices General offices Reading poor reproductions Reading ink handwriting Reading high-contrast print Draf+tirg rooms Detailed drafting Rough layout drafting Service Areas Stairways, landings, doorways Lobbies Toilet rooms I llu minance category D E F G H D E H F D D F E C C C Source: A comprehensive table given in the sixth edition of the IES Lighting Handbook. lighting designers wanted to know the recommended illuminance for a given task, they would look in the IES Lighting Handbook to find a recommended level and then design an illumination system for the task using the recommended level as a minimum. This procedure provides very little latitude for fine-tuning lighting design. The new method for determining required illuminance provides three categories based on the room function and visual task available to the designers. They are 1) rooms involving visual tasks for which there are tables of prescribed illuminance; 2) rooms involving-visual tasks for which there are tables of measured visibility, or for which visibility can be measured; 3) rooms not involving visual tasks. In each case, a more comprehensive investigation of required illuminance is performed according to the following steps. a) Instead of a single recommended illuminance value, a category letter is assigned (Table I). b) The category letter is used to define a range of illuminance (Table II). c) From within the recommended range of illuminance, a specific value of illuminance is selected after consideration is given to the average age of workers, the importance of speed and accuracy, and the reflectance of task background. The importance of acknowledging the speed and accuracy with which a task must be performed is readily recognized. Less obvious is the need to consider the age of workers and the reflectanee of task background. To compensate for reduced visual acuity, more illuminance is needed. Using the average age of workers as the age criterion is a compromise between the need of the younger and the older workers and, therefore, a valid criterion. Task background affects the ability to see because it affects contrast, an important aspect of visibility. More illuminance is required to enhance the visibility of tasks with poor contrast. Reflectance is calculated by dividing the reflected value by the incident value. The data- given in Tables Ill and IV are taken from the IES handbook and are applied to provide a single value of illuminance from within the recommended range.
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