CRI MEANING LIGHTING | WHAT IS CRI | CRI VALUE OF LAMPS

CRI MEANING LIGHTING
When light falls on an object, it is a measure of the amount of light that shows off its natural color. The color rendering index (CRI) is the magnitude of the light source that most accurately displays the color of a surface.
WHAT IS LUMEN
The output of light is measured in lumens or luminous flux
When a light source with a candela intensity is set at the center of the sphere with a meter radius, the amount of light source that falls on each m2 area on the surface of the sphere is one lumen
LUX
The illumination of a surface is measured in lux. 1 m? The size of the lumen in an area is a lux
Load Circuit Efficiency
When a lamp consumes 1 watt of power, the number of lumens it emits is lamp circuit efficiency
Colour Rendering Index
When light falls on an object, it is a measure of the amount of light that shows off its natural color. The color rendering index (CRI) is the magnitude of the light source that most accurately displays the color of a surface
Lamps | Lamp watts including ballast watts | Efficiecy Including ballest lumen per watt | Colour Rendering Index | Lamp life burning Hours |
Incandescent Lamp | 15,25,40,60,75,100,150, 200,300,500 | 8 to 7 | 100 | 1000 |
Fluorescent Lamp | 18,20,36,40 | 30 to 80 | 65 to 77 | 5000 to 15000 |
Halogen | 200,300,500,750,1000, 1500,2000 | 16 to 23 | >90 | 2000 to 4000 |
Compact Fluorescent Lamp | 8,12,15,28,32,45 | 26 to 60 | 80 | 8000 to 10000 |
High pressure Mercury Vapour lamp | 80,125,250,400,1000, 2000 | 50 to 60 | 45 to 60 | 5000 to 8000 |
Metal halide lamp | 70,150,250,400,1000 | 50 to 70 | 70 | 8000 to 12000 |
High pressure Sodium Lamp | 70,150,250,400,1000 | 80 | 25 to 60 | 12000 to 20000 |
Low Pressure Sodium Lamp | 35,55,135 | 90 to 100 | 40 to 60 | 12000 to 24000 |
Light System Designing
When designing a lighting system, one must first determine the amount of lux required. It depends on where it can be installed and how it works. For example the lux level for street lighting and office lighting will be different
Interior type | Service Range | Remarks |
General office | 300–500-700 | |
Computer work station | 300–500-750 | |
Conference Room, Executive office | 300–500-750 | |
Bank Counter, Office Area | 300–500-750 | |
Public Area,Banks | 200–300-500 | |
Auditorium,hotel | 50–100-150 | There should be a facility for dimming the lights. Special lights should be set up in the areas between the seats |
Entrance hall | 50–100-150 | |
Reception, Cashier’s and Porter’s desk | 200–300-500 | Appropriate lights should be set in specific areas |
Bars,cofee base dining airport | - | Design the lights to suit the ambient conditions |
Bedroom | 30–50-100 | Lights should be set up in addition to the bedside table and desks |
Bathroom | 50–100-150 | It is desirable to set the lights in addition to the proximity of the face mirrors |
Energy conservation for tighting should be considered when designing to set up a workshop, home, or business. The best way to conserve energy for lighting is to use as much natural light as possible
The amount of light set up in work areas should be higher than that set in common areas. This should be done while designing the system
Estimate the number of light fittings taking into account the above. To estimate the number of light fittings, first find the room index
Different Energy Savings
Natural Day Light

Businesses that use naturally available light during the day. It can reduce the energy required for lighting for industrial and public buildings
Natural day light can be used by placing specially designed glass on the roofs of buildings at specific intervals
Large glass windows can be set up in office rooms to use natural light. In addition, although natural light can be used more in other ways, in factories and offices, each method can be implemented depending on the facilities set up while designing the building
This saves a great deal of energy used by the skill of the architects who design the buildings
Light Fixture Reduction

You can set timers on one of the streetlights and switch off the lights at certain times of the night
This can save energy. Setting up good reflectors and increasing the illumination can also reduce the number of light fittings. Painting the walls and ceiling well can increase the amount of light that is reflected
Similarly you can increase the retact as light depending on the choice of floor tiles to be embedded in the floor. Another way is to set more lights in the work area and less lights in common areas to reduce the number of light fittings
High Efficiency Lamps

Illumination should be done using lamps with color rendering index in the areas where the correct color is to be expressed. Color rendering indices for GLS and halogen lamps are above 100 and 90, respectively. Thus it is appropriate to use these types of lamps where the color should be properly expressed
However, the efficiency of these lamps is very low. Therefore a large number of lamp fittings will be required. This will increase the amount of power used.
Metal halide lamps have a lower color rendering index than GLS and halogen lamps. But their efficiency is very high. The efficiency of sodium vapor lamps is higher than that of metal halide lamps
But the color rendering index is low. Therefore, it is more appropriate to use metal halide lamps where the color needs to be properly expressed
Similarly, sodium lamps can be used for streetlights where it is not necessary to express the correct color. Their efficiency is higher than other lamps
LED lamps are used as the next generation lamps. But these are still in the process of being expanded. These types of lamps are currently used in the following locations
- Used as indicating lamps on electrical panel boards
- Used in traffic signal lights
- Used as light in aircraft
- Used in emergency lights
- Used in decorative lighting
- Used in portable lamps
EFFECT OF REDUCTION IN SUPPLY VOLTAGE ON ENERGY CONSUMPTION
When the supply voltage is reduced, the amount of power consumed by all types of lamps decreases. But the voltage must be reduced to the extent that the lamps do not flickering
Using transformers and reactors, the voltage can be reduced to operate at a specific voltage at a given time. Reducing the amount of voltage will reduce the output of the lights
Therefore, it should be set to operate at a lower voltage when more light is not required. This also reduces the energy for usable lights
ELECTRONIC BALLAST AND LOW LOSS ELECTROMAGNETIC CHOKE
Ballasts, which are usually used to light lamps, take 15 to 20 watts of power. But electronic ballasts consume approximately 1 watt of power
The downside of electronic ballast is that it injects unnecessary harmonics into the system. It costs 1.5 to 2 times more than regular ballasts. Other types of vacuum impregnated copper ballasts are used
These can take up to 7 watts of power. And its low cost. 6. Programmed timers using TIMERS AND OCCUPANCY SENSORS Micro controllers are now widely available in the market
You can set the timer’s ON and OFF time and switch off the lights when the ligth is not required. Lights can also be switched off using infra red occupancy sensors
Other types of ultrasonic sensors are not available in India. Occupancy sensors can be connected to micro controllers to switch off the lights when no one is in the room. It may be helpful to use occupancy sensors in areas where people occasionally use them
FLUORESECENT TUBE LIGHTS

The types of fluorescent tube lights are as follows
- T12: 40 watts, the diameter of the tube is 12⁄8 “i.e. 33.8mm
- T8: 36 watts, the diameter of the tube is 8/8 “i.e. 26mm
- T5: 14, 21,28, 35 watts, the diameter of the tube is 5⁄8 ”i.e. 16mm
T5 diameter tube light is shorter in length than T8 and T12 diameter tubes. Thus T5 lamps with higher lamp efficiency are 50mm shorter than 8 and 12 lamps
Also it only runs on electronic choke. Therefore, when fitting 75 lamps in fittings with 12 and T8 light, special arrangements are required
The efficacy of a 35 watts 15 lamp is 95 lumens / watt. But for 18 lamps it will be 89 lumens / watt, with electronic choke. Mercury with glass does not absorb as the T5 lamp has a coating on the inside of the glass
Thus the use of mercury will be greatly reduced
CFL LAMPS

The color rendering index of CFL lamps is greater than 80. And their output is 55 to 67 lumens / watt
CFL lamps are commonly used for floor illumination in showrooms, artefacts, hotels, etc. CFL lamps are more efficient than GLS and halogen lamps
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