Question 1

What is Maintenance factor (MF)?

Accepted Answer

Maintenance factor (MF) is a concept in lighting design. It refers to the ratio between the average illuminance or average luminance on a specified surface after a lighting device has been used for a certain period of time and the average illuminance or average luminance on the same surface when the device is newly installed. Because during the use of the lighting device, due to the light decay of the light source, the decrease of the light transmittance of the lens, and the environmental pollution of the lamp, the light(luminous flux) emitted by the lamp will attenuate and the lighting effect will deteriorate. Therefore, when doing lighting design, we should appropriately increase the design value to balance the overall light decay of the lamp in the future.

Question 2

How to get the value of Maintenance factor (MF)?

Accepted Answer

For street lighting, we can use 0.8, and it’s normally 0.9 for sports lighting which is finally depending on the design of lamps and application.

MF = LLMF x LEF x LODV x LODR x LODL x LMF

LLMF = Lamp Lumen Maintenance Factor [from the luminaire supplier – using the DOE TM21-11 calculator, LM80 chip data and ISTMT in-luminaire LED temperature, for 85,000 hours at 25C ambient]

LEF = Luminaire Electronic (Failure) Factor [Normally at 0.99]

LODV = Luminaire Optical Depreciation Factor for Visor [Visors normally means glass cover or others]

LODR = Luminaire Optical Depreciation Factor for Reflector

LODL = Luminaire Optical Depreciation Factor for Lens [Normally PC, PMMA and others]

LMF = Luminaire Maintenance Factor [Set at 0.92 if there is a Visor or 0.78 if there is no Visor]

Question 3

Maintenance factor (MF) calculation reference table

Accepted Answer

The calculation refers to the second point above, and the standard refers to the table below.

Question 4

Lux to lumens conversion

Accepted Answer

The relationship between the two: 1 lux =1 lumen (lm)/square meter =1cd×sr/ square meter
(lux = lm / m2)

Physics concepts:
Lumen (lm) is a physical unit describing the luminous flux, which is explained by the physical interpretation of a candle (cd, Candela, a unit of luminous intensity, equivalent to that of an ordinary candle) at a solid Angle (a unit sphere with a radius of 1 meter, the Angle represented by the cone corresponding to the crown of a 1 square meter sphere, The corresponding central Angle of the middle section is about 65°).
lux (legal symbol lx) is a unit of Illuminance. When the luminous flux of an object uniformly illuminated by light is 1 lumen over an area of 1 square meter, its illuminance is 1 lux.

Question 5

Watts or lumens?

Accepted Answer

Lumens measure the total amount of light emitted by a light fixture, while watts measure the amount of electricity a light fixture consumes. Wattage doesn't tell you exactly how bright a light fixture is, lumens do. If the luminous efficacy of the luminaire is consistent, the brightness of the luminaire is easy to estimate, because luminous flux = wattage * luminous efficacy, that is, the higher the power level, the more light it emits.

Question 6

W to Lumens

Accepted Answer

For instance, a 3 watt LED bulb made by one company might produce more light (lumens) than one made by another company. ZGSM LED Lighting recommendations are based on the fundamental principle that 1 watt of power will produce approximately 10 lumens of light.

Question 7

Lumens to Watts

Accepted Answer

20 Watts of Lumens, A 1W LED light bulb is equivalent to 20 lumens. The type of light source being utilized must be taken into account when converting 20 lumens to watts since the higher the efficiency, the higher the lumen level produced per watt of power used.

Question 8

lux v lumens

Accepted Answer

One lux (1 lux) is defined as one light dispersed over a surface area of one square meter. In other words, a specification in lux will tell you how many Lumens (total light output) are required to adequately illuminate the measured area.1 lux to lumens, One lux is equivalent to one lumen per square meter, or the amount of light in a certain area. The quantity of light produced in a specific area is measured in lux. One lumen per square meter is equivalent to one lux.

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