Choosing and planning the proper lighting goes beyond providing sufficient illumination. The past few years have seen a steep rise in awareness about our bodies’ Circadian rhythm and how external lighting can affect our biological cycle. It is now rampant that blue lighting (emitted from mobile and computer screens) plays a role in raising alertness, but it is not optimal for relaxing. But, light that is too bright can intensify emotions, and dimmed lights can disrupt vision.
Evidently, in lighting, every luminaire has its place. To fit the function, the approach needs to be objectively tailored. We need to focus as much as we need to lie back, right? Today, this challenge is even more nuanced. Our homes or offices do not cater to a pure function. In a single space, we need it all. We require illumination conducive to day-to-day tasks (Ambient Lighting), appropriate for carrying out tasks (Task Lighting) and spotlighting key features (Accent Lighting). The need of the hour is to strategise and light a space in layers.
To further optimise a lighting plan, one must understand what ‘weightage’ each layer must have. Workspaces are function-heavy areas, while restaurants are more ambient-centric. Interior designers often consider the occupant’s subjective, psychological experience (the qualitative aspect of light). However, they fail to assess a space’s light requirements (quantitative aspect) directly influencing emotional stimulation. The first step in comprehending the latter is understanding the basics.
“Our homes or offices do not cater to a pure function. In a single space, we need it all. We require illumination conducive to day-to-day tasks (Ambient Lighting), appropriate for carrying out tasks (Task Lighting) and spotlighting key features (Accent Lighting). The need of the hour is to strategise and light a space in layers.”
Terms to Know
Build Your Lighting Vocabulary
Lumens (lm), simply put, is a measure of the brightness of a lighting fixture. Pedantically, lumens is the measure of the total amount of visible light (to the human eye) from a lamp or light source.
Fun fact: In theory, LED and Incandescent bulbs with the same lumens each provide the same brightness. However, Incandescent bulbs emit more light and use more energy to produce the same effect. On the other hand, LEDs reveal the objects’ colours more precisely because a higher percentage of the directional light emitted by them is reflected off objects and enters the pupil.
Lux is the intensity of the brightness of a lighting fixture; it is the light measured one metre away from a light source. To distinguish lumens from lux, one can think of lumens as the light emitted by a bulb and lux as the amount of light that hits objects. Lux is measured in lumens per metre square (lm/m2).
Alternatively, foot-candle is also a measure of brightness intensity. It is measured in lumens per square foot (lm/ft2). 1 Footcandle (FC) = 10.76 Lux (lx)
Wattage (measured in Watts) refers to the energy required to achieve the specified lumens.
The Lumens Method
Armoury Set, Time to Light it up!
IES (the largest society of professional lighting designers) provides an invaluable resource. They have issued a lux/footcandle chart that specifies the standard for the amount of foot candles and lux humans need to perform tasks comfortably in different spaces. It breaks the lux/footcandle required for each room into ambient and specific task-focused requirements. For example, it stipulates that the ambient lighting a kitchen requires is 108 lux, but for activities such as chopping on the counter, an illumination of 538 lux is advised.
Click here for Corporate and Hospitality Standards
Step 1: Calculate the area of the room and sub-areas where tasks will take place. (Eg. area of a desk to be utilised for reading)
Step 2: Establish the footcandle requirement(s) for your application
💡 Add 10 extra foot candles/110 extra lux if the space has dark walls.
Step 3: Multiply the area of the room by footcandle requirements to know the lumens needed by the space in question.
💡Remember to use compatible SI units
Step 4: Divide the resultant lumens by the number of lumens your choice luminaire generates (check the product packaging or company website for details). Voila! Now you have the number of fixtures required.
“In the era of state-of-the-art technology, the Lumens Method is a calculation that can help one quickly arrive at estimates. It doesn’t account for phenomena such as the direction distribution of a luminaire that allows it to conserve energy or consider Light Loss Factors (LLF). It assumes that all fixtures are on the ceiling, and doesn’t accommodate for different positions that light can be fixed in, like wall-mounted or pendant-hung. ”
Is the Lumens Method enough?
Calculators in the Age of Supercomputers?
The Lumens Method is the most popular and hassle-free way to calculate the lighting a room requires. But it also comes with its assumptions.
1) All the luminaires in the room shall be the same and have the same orientation
2) The luminaires will not have a directional distribution and are aimed directly at the floor
3) The luminaires will be arranged in a uniform array on the ceiling and have the same mounting height
In the era of state-of-the-art technology, the Lumens Method is a calculation that can help one quickly arrive at estimates. It doesn’t account for phenomena such as the direction distribution of a luminaire that allows it to conserve energy or consider Light Loss Factors (LLF). It assumes that all fixtures are on the ceiling, and doesn’t accommodate for different positions that light can be fixed in, like wall-mounted or pendant-hung.
Radiosity and Ray Tracing Calculations
The V-Ray of Lighting Design
It would be blasphemous if we didn’t have more accurate and detailed ways to calculate optimal lighting in this day and age. Computer methods, namely Radiosity and Raytracing, predict the illumination at specific points in the space (“point-by-point” illumination). Most software programs even offer a perspective rendering of the illuminated space.
Radiosity is a fast calculation method that assumes all room surfaces have a Lambertian finish that diffuses light perfectly. Raytracing is slower but considers both Lambertian and specular reflections. Some software programs leverage the best of both worlds. They employ radiosity for speedy calculations of most lighting effects and then perform a raytracing “layer” to create more realistic images. With enough time, computer calculations can produce impressive reports and renderings.
Left to Right: Radiosity and Ray Tracing
“Radiosity is a fast calculation method that assumes all room surfaces have a Lambertian finish that diffuses light perfectly. Raytracing is slower but considers both Lambertian and specular reflections. In addition, these methods can inculcate directional luminaires, different types of lighting products, irregular fixture placements, and more. Lighting software requires special training and experience. With modest training, calculations of rectangular box-shaped spaces can be rapid. Nonetheless, an expert is still needed when designs are more complex and detailed. “
In addition, these methods can inculcate directional luminaires, different types of lighting products, irregular fixture placements, and more. Lighting software requires special training and experience. With modest training, calculations of rectangular box-shaped spaces can be rapid. Nonetheless, an expert is still needed when designs are more complex and detailed.
The Lumens Method or even learning the basics of Radiosity and Raytracing cannot replace the experience or agency of Lighting Designers. The Lumen method, specifically, aids in arriving at a ballpark. With these calculations, one can collaborate with Lighting Designers from a more informed position.
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Date added:
8 September, 2023
