Light Level, also referred to as Illuminance, represents the amount of light that is measured on a surface (which is plane). Or, it can be described as the total luminous flux incident that strikes on a plane surface. It is measured per unit area and is commonly known as LUX.
Understanding LUX
LUX, also called DIALux is increasingly becoming popular in the modern world. You can now plan in DIALux with great luminaires from the world’s most renowned manufacturers and enjoy ultimate freedom in the lighting design process.
Benefits of LUX
Featuring professional light planning, LUX is extremely simple and effective. It utilizes the latest luminaire data and state-of-the-art software that’s always available for free. The colored light scenes with light emitting diodes (LED) are energy efficient and guarantee excellent illumination for all your buildings including outdoor spaces.
Recommended LUX Levels
The level of lighting in the outdoor is approximated to be 10,000 lux, albeit on a normal, clear day. However, for a building, especially in the areas that are closer to windows, the LUX levels may possibly be reduced to 1,000 lux. On the other hand, the middle area may register a 25 – 50 lux. Consequently, you may need additional lighting equipment to compensate for these low levels. For precision & detailed works, the level of light may range between 1500 to 2000 lux.
In homes– The recommended illumination levels for homes is often 150 lux. The living and dining rooms may work pretty well with about 25 to 50 lux.
Supermarkets– Working spaces like supermarkets and mechanical rooms require light levels of about 750 lux.
In offices– The normal workstation requires 500 LUX while the ADP area and conference rooms require 500 LUX and 300LUX respectively. The auditorium requires 150-200 LUX while the training room and internal corridors should be supplied with 500 LUX and 200 LUX respectively.
The table below represents the light levels for different workspaces.
Activity | Illumination(Lux, lumen/m2) |
Public areas featuring dark surroundingsrecommended | 20-50 |
Warehouses, theaters, homes, archives | 150 |
Simple orientation meant for short visits | 50-100 |
Working areas involving occasional visual tasks | 100-150 |
Easy classes | 250 |
Showrooms, normal office work, a study library, PC works | 500 |
Detailed drawing and mechanical work, operation theaters | 1,000 |
Supermarkets, office landscapes | 750 |
Performance of prolonged & exacting visual tasks | 5000-10000 |
Performance of extremely special visual activities of very low contrast & small size | 10000-20000 |
Factors Affecting the Effectiveness of Illumination
The effectiveness of illumination is usually affected by several factors, including light quantity & quality, contrast, amount of flicker, shadows, and intensity of glare. To optimize illumination in security, emergency, and safety situations, consider adjusting each factor differently. Lighting standards also play an important role in the design, installation, durability, and efficient distribution of illumination.
Measuring and stimulating Light Level – Illuminance
Illuminance is measured in foot candles (ftcd, fc, fcd) or lux (in the metric SI system). A foot candle is actually one lumen of light density per square foot; one lux is one lumen per square meter.
• 1 lux = 1 lumen / sq. meter = 0.0001 phot = 0.0929 foot candle (ftcd, fcd)
• 1 phot = 1 lumen / sq. centimeter = 10000 lumens / sq. meter = 10000 lux
• 1 foot candle (ftcd, fcd) = 1 lumen / sq. ft. = 10.752 lux
Calculating Illumination
Illumination is calculated using the formula = Ll Cu LLF / Al (1). In this formula, I denotes illumination (measured in lux, i.e. lumen per m2), Ll represents lumens/ lamp (i.e. lumen), Cu is the coefficient of utilization, while LLF is light loss factor and Al is the area/ lamp (measured in m2).
Light Planning: The Steps
Light planning is a five-step process. The actual process involves:
- Planning objective analysis
- Planning conditions analyses
- Overall planning
- Detailed planning
- Documentation
Understanding Glare
Glare can be categorized into two groups: discomfort and disability glare. The level of discomfort glare can be measured by determining the glare index in accordance to the UGR method. This is often graded on a scale, which ranges between 13 and 28 where the greater the glare index the greater the degree of glare. The smallest variation in the glare index designating a significant difference is three.
Reflections from reflective glare or materials can usually be avoided by adopting the following strategies:
· Choosing convenient luminaire positioning
· Using materials for all reflective surfaces
· Selecting fixture with effective screening and low luminous intensity
· Picking out luminaires with a bigger surface area
· Choosing light colors for your ceilings and walls
Balance is key
A well-balanced luminance is essential to boost visual clarity, effectiveness of the ocular functions of the eye, and contrast sensitivity. You should always avoid high luminance which can cause glare, intense luminance contrasts that may cause visual tiredness, and low luminance contrasts, which trigger a staid atmosphere that doesn’t stimulate.
