Lecture 5 - Visual Sense Student PDF

11/1/2024 VISUAL SENSE ETYMOLOGY OF LIGHT The “light” that refers to illumination comes from the Indo-European root leuk- (bright, brightness), source of the prehistoric Germanic leukhtam (to produce light) and the Old English léoht (bright)....

11/1/2024 VISUAL SENSE ETYMOLOGY OF LIGHT The “light” that refers to illumination comes from the Indo-European root leuk- (bright, brightness), source of the prehistoric Germanic leukhtam (to produce light) and the Old English léoht (bright). 1  11/1/2024 WHAT IS LIGHT? Visible Light, commonly refers to electromagnetic radiation that can be detected by the human eye. LIGHTING ERGONOMICS Lighting ergonomics is the relationship between the light source and the individual. It has a significant effect on productivity, workplace wellness and preventing CVS (a condition resulting from focusing the eyes on a computer for prolonged periods of time). 2  11/1/2024 COMPUTER VISION SYNDROME (CVS) is a condition resulting from focusing the eyes on a computer or other display device for protracted, uninterrupted periods of time and the eye's muscles being unable to recover from the constant tension required to maintain focus on a close object. REMEMBER THE 20-20-20 RULE! 3  11/1/2024 COMMON LIGHTING PROBLEMS Insufficient light – not enough (too little) light for the need.. Improper contrast. Poorly distributed light. Flicker. Glare – too much light for the need GLARE Glare is what happens when a bright light source or reflection interferes with how you are 'seeing' an object. In most cases, your eyes will adapt to the brightest level of light. 4  11/1/2024 REFLECTED GLARE DIRECT GLARE Reflected glare is caused by: Direct glare is caused by: Light reflected from polished, Very bright light from shiny or glossy surfaces. poorly positioned light Glass on picture frames, or fixtures. windows at night. Sunlight. Monitors / screens. HOW DO YOU DETECT GLARE? 5  11/1/2024 GOOD LIGHTING IN THE WORKPLACE PROMOTES: a reduced risk of occupational accidents and health problems; better concentration and accuracy in work; a brighter, cleaner workplace resulting in a more active, cheerful environment; improved work performance; better visibility, improved accuracy and increased work speed enhancing production. TIPS IN MANAGING LIGHTING FOR COMFORT 6  11/1/2024 1. Make Full Use of Daylight/Natural Lighting Natural lighting is most effective in improving illumination. Using daylight improves morale and it is free. However, it can also create problems with glare on your monitor. To avoid this, position your desk to the side of the window. Here are some tips on how to use natural lighting provide skylights, for example by replacing roof panels with translucent ones; equip the workplace with additional windows; place machines near windows; move work requiring more light near windows. 7  11/1/2024 2. Use of Local Light The use of local light has many advantages. Local lighting requires less power to get adequate brightness since brightness is decreased exponentially by the distance from a light source. Here are some tips on how to use local lighting: place and direct light the way it seems best for the work being performed; light up the spot where light is needed; 8  11/1/2024 3. Paint Ceilings and Walls in a Light Color Light colors create more reflection than dark colors. Light colors make it easier to keep ceilings and walls clean. Glossy white painted surfaces reflect 100% of the light whereas black surfaces reflect no light at all. To achieve improved illumination, follow these recommendations: use white or a very light color on ceilings; paint walls white; use light or half-tone colors on tables and machines. 9  11/1/2024 4. Choose an Appropriate Background The background at the workstation is important, especially for visual tasks that demand close, continuous attention. A simple background will allow for more accuracy and an increase in production whereas a complex background may disturb the work and increase the workload. To obtain an optimum visual task background: 1. eliminate potential sources of distraction, such as posted papers, forms or schedules on walls; 2. use light-colored partitions and screens to eliminate or screen sources of distraction; 3. select an appropriate color for the work background. 10  11/1/2024 The following table provides some guidance for making the selection: LIGHTING STANDARDS 11  11/1/2024 AMOUNT OF LIGHT NEEDED FOR VARIOUS TASKS The amount of light we need varies and depends on: Type of task being done (such as demands for speed and accuracy). Type of surfaces (does it reflect or absorb light). General work area. Individual's vision. Take note : The amount of light falling on a surface is measured in units called lux. Lux = Lumens (quantity of light) per square meter. AMOUNT OF LIGHT NEEDED FOR VARIOUS TASKS Min Illumination Class of Visual Task Typical Examples of task (lux) Boilerhouse (coal and ash handling); dead storage of Casual Seeing 100 rough, bulky materials; locker rooms Rough, intermittent bench and machine work; Ordinary rough tasks 150 rough inspection and counting of stock parts; assembly of heavy machinery Medium bench and machine work, assembly and Moderately critical tasks 300 Inspection; ordinary office work such as reading, writing, filing Fine bench and machine work, assembly and Critical Tasks 700 inspection; extra-fine painting, spraying; sewing dark-coloured goods Assembly and inspection of delicate mechanisms; Very Critical tasks 1500 tool- and die-making; gauge inspection; fine grinding work Exceptionally difficult or 3000 or more Fine watchmaking and repairing important tasks 12  11/1/2024 Recommended REFLECTANCE for offices DEFINITION OF TERMS 13  11/1/2024 refers to the quantity of light emitted per LUMINOUS second in a specific INTENSITY direction which is measured as candela (cd). Incandescent lamp Fluorescent lamp 10 lm/W 100 lm/W is the measure of the total light emitted by a light source in all direction., LUMINOUS which is measured in lumens (lm). FLUX 14  11/1/2024 or simply Brightness 1 foot candle = one lumen per square foot or 10.764 lux. Working with luminous flux requires the use of a solid angle measure called the steradian (sr). Area SR = r2 15  11/1/2024 11 What solid angle is subtended at the center of a sphere by an area of 1.6 m2? The radius of the sphere is 5 m. A. 0.061 sr B. 0.062 sr C. 0.063 sr D. 0.064 sr PROBLEM: What solid angle is subtended at the center of a sphere by an area of 1.6 m2? The radius of the sphere is 5 m. Area 1.6m2 Solid Angle = 2 = = 0.064 𝑠𝑟 r 5m2 16  11/1/2024 IMPORTANT NOTE! A source having an intensity of one candela emits a flux of one lumen per steradian. 𝑇𝑜𝑡𝑎𝑙 𝐹𝑙𝑢𝑥 = 𝐼 x 4𝜋 𝐹𝑙𝑢𝑥 = 𝐼 𝑥 (𝑆𝑜𝑙𝑖𝑑 𝑎𝑛𝑔𝑙𝑒) 17  11/1/2024 12 A 30 cd spotlight is located 3 m above a table. The beam is focused on a surface area of 0.4 m2. Find the intensity of the beam. A. 8490.77 cd B. 8491.77 cd C. 8492.77 cd D. 8493.77 cd PROBLEM: A 30 cd spotlight is located at a radius of 3 m above a table. The beam is focused on a surface area of 0.4 m2. Find the intensity of the beam. 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐹𝑙𝑢𝑥 = 30 𝑐𝑑 𝑥 4𝜋 = 376.99 𝑙𝑢𝑚𝑒𝑛𝑠 Finding Intensity of the Beam Area 0.4 m2 Solid Angle = = = 0.0444 𝑠𝑟 r2 3m 2 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐹𝑙𝑢𝑥 376.99 𝑙𝑚 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = = = 8490.77 𝑐𝑑 𝑆𝑜𝑙𝑖𝑑 𝐴𝑛𝑔𝑙𝑒 0.0444 𝑠𝑟 18  11/1/2024 Illuminance is the quantity of light on a unit of surface and measured as lux. 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐹𝑙𝑢𝑥 𝐼𝑙𝑙𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 13 A 400 cd light is located 2.4 m from a tabletop of area 1.2 m2. What is the illumination? A. 68. 44 lux B. 69.44 lux C. 70.44 lux D. 71.44 lux 19  11/1/2024 PROBLEM: A 400 cd light is located at a radius of 2.4 m from a tabletop of area 1.2 m2. What is the illumination? 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐹𝑙𝑢𝑥 = 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝑥 𝑆𝑜𝑙𝑖𝑑 𝐴𝑛𝑔𝑙𝑒 𝐴 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐹𝑙𝑢𝑥 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝑥 2 𝐼𝑙𝑙𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = = 𝑟 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 1.2 400 𝑐𝑑 𝑥 2.4 2 𝐼𝑙𝑙𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = = 69.4444 𝑙𝑢𝑥 1.2 14 A luminous flux of 320 lumens falls on a square with an area of 20 cm on a side. What is the illuminance of the square? A. 5000 lux B. 6000 lux C. 7000 lux D. 8000 lux 20  11/1/2024 PROBLEM: A luminous flux of 320 lumens falls on a square with an area of 20 cm on a side. What is the illuminance of the square? 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐹𝑙𝑢𝑥 320 𝐿𝑢𝑚𝑒𝑛𝑠 𝐼𝑙𝑙𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = = = 8000 𝑙𝑢𝑥 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 (0.20 𝑚)2 Luminance is the amount of light emitted/reflected by a surface. Unit of measurement is CANDELA PER SQUARE METER (CD/M2) LUMINANCE 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = OR 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 cos θ 𝑥 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 21  11/1/2024 15 A plane Lambert radiator is a square 2 mm on a side with luminance 400 cd/m2. What is the intensity of the radiator viewed along the line (a) normal to its surface, and (b) 30° from the normal to its surface? A. 0.0014 cd B. 0.0015 cd C. 0.0016 cd D. 0.0017 cd PROBLEM: A plane Lambert radiator is a square 2 mm on a side with luminance 400 cd/m2. What is the intensity of the radiator viewed along the line (a) normal to its surface, and (b) 30° from the normal to its surface? 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 400𝑐𝑑 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 𝑥 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 = 𝑥 (0.002𝑚)2 = 0.0016 𝑐𝑑 𝑠𝑞𝑢𝑎𝑟𝑒 𝑚𝑒𝑡𝑒𝑟 22  11/1/2024 16 A plane Lambert radiator is a square 2 mm on a side with luminance 400 cd/m2. What is the intensity of the radiator viewed along the line (a) normal to its surface, and (b) 30° from the normal to its surface? A. 0.0014 cd B. 0.0015 cd C. 0.0016 cd D. 0.0017 cd PROBLEM: A plane Lambert radiator is a square 2 mm on a side with luminance 400 cd/m2. What is the intensity of the radiator viewed along the line (a) normal to its surface, and (b) 30° from the normal to its surface? 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = cos θ 𝑥 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 400𝑐𝑑 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 𝑥 cos θ 𝑥 𝑈𝑛𝑖𝑡 𝐴𝑟𝑒𝑎 = 𝑥 (0.002𝑚)2 𝑥 cos(30𝑜 ) 𝑠𝑞𝑢𝑎𝑟𝑒 𝑚𝑒𝑡𝑒𝑟 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 0.0014 𝑐𝑑 23  11/1/2024 Contrast is the relationship between the brightness of an object and its background. The average contrast should be above 0.5. CONTRAST Reflectance is the ratio of light falling of the luminance and illuminance at a surface. REFLECTANCE 17 What is the luminance of a surface having a 50% reflectance and 4 foot candle illumination? A. 1 foot lambert B. 2 foot lambert C. 3 foot lambert D. 4 foot lambert 24  11/1/2024 PROBLEM: What is the luminance of a surface having a 50% reflectance and 4 foot candle illumination? 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑎𝑛𝑐𝑒 = 𝐼𝑙𝑙𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 𝐿𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = 𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑎𝑛𝑐𝑒 𝑥 𝐼𝑙𝑙𝑢𝑚𝑖𝑛𝑎𝑛𝑐𝑒 = 0.5 𝑥 4 𝑓𝑜𝑜𝑡 𝑐𝑎𝑛𝑑𝑙𝑒 = 2 𝑓𝑜𝑜𝑡 𝐿𝑎𝑚𝑏𝑒𝑟𝑡 25  11/1/2024 BASIC COMPUTATION IN ILLUMINATION (How many lights do we need?) LIGTING CALCULATION Calculate the size (area) of your room. To get the total area of your room, you need to multiply its length and width. For this example, we will get the lighting computation of our Bedroom. 26  11/1/2024 Determine the “Lux/Foot-candle” needed by your room. To determine the Lux/Foot-candle needed for various rooms. Refer on the table below. ROOM FOOTCANDLES LUX BATHROOM 20 - 50 215 – 540 BEDROOM 10 - 20 110 - 215 DINING ROOM 10 – 20 110 – 215 ENTERTAINMENT 10 – 20 110 – 215 ROOM HALLWAY 5–7 55 – 75 KITCHEN (basic 20 - 50 215 – 540 lighting) KITCHEN (food 50 -100 540 -1075 prep) LIVING ROOM 10 -20 110 -215 For our example: The foot-candles needed for a bedroom = 10 -20 foot-candles Calculate the required LUMENS of your room. Lumens is acquired by multiplying the total number of foot- candles (from dimmest – brightest) by the area of your room. For our example: 4,000 27  11/1/2024 Determine what type of bulb should be used on your computed amount of lumens. A Compact incandescent lamp has 40 – 70 lumens per watt An incandescent light has 10 -17 lumens per watt For our example: (We will be using a 20 watts Compact incandescent bulb = 1200 lumens) 4,000 3.33 or 4 bulbs 28  11/1/2024 ACTIVITY NO. 2: MEASURING LIGHT A. Using your Lux meter, record the light level in the following reference points and write the result in the table below: REFERENCE POINT MEASUREMENT (IN LUX) Flashlight Max screen light of laptop Max screen light of cellphone Direct Sunlight (Open grounds) Laboratory Building (Engineering Faculty) Laboratory Building (Basement - Canteen area) Laboratory Building (1 classroom only) Comfort room (Near gymnasium) Elevator Academic Building (1 classroom facing the OG) 29