Tips for choosing light intensity
Generally speaking, luminous intensity translates as the ability of a light source to illuminate a specific direction. It is one of the 7 photometric quantities that form the basis of all lighting measurements. However, these quantities are often the subject of confusion.
In this context, a few clarifications on the characteristics of the main photometric quantities that are frequently confused with luminous intensity are in order. Before determining how to choose the right luminous intensity for a luminaire, discover the different lamp technologies and in particular, the specifics of the LED lamp.
Understanding luminous intensity
Luminous intensity is usually confused with other photometric quantities, notably luminous flux, illuminance and luminance. It is therefore necessary to distinguish between these notions.
What is luminous intensity?
Expressed in Candela (Cd), luminous intensity measures the amount of light scattered by a light source at a specific direction. Derived from a Latin word, this unit of measurement mainly means "candle". In this context, a candela is equivalent to luminous intensity or the amount of light scattered by a candle in a horizontal direction.
This quantity does not take into account the viewing distance from the directive source, but the amount of light emitted by it. This implies that regardless of the distance separating the latter from its observer, the value of the luminous intensity of the illumination remains the same.
What's the difference between luminous intensity and luminous flux?
Luminous intensity expresses the amount of light emitted by the light source in a specific direction. Expressed in Lumen (lm), luminous flux, meanwhile, represents the amount of light diffused by the luminaire overall.
The "brightness" or luminosity of a bulb increases as the luminous flux, or number of lumens, rises.
Distinguish between luminous intensity and illuminance
Expressed in Lux, illuminance represents the quantity of light received by the illuminated area. It quantifies the number of luminous fluxes per square meter, i.e. the quantity of Lumens per square meter (1 Lux = 1 Lumen/m²).
Unlike luminous intensity, illuminance varies according to the distance separating the light source from the illuminated area. When the light source approaches the illuminated area, the surface area decreases and the amount of light it receives increases, and when it moves away from it, the opposite phenomenon occurs. In this case, the illuminated area increases and the amount of light it receives decreases.
Luminous intensity and luminance: not to be confused
Luminance is the only photometric quantity that humans can perceive. Expressed in candela/m², it quantifies the luminaire's glare. Like luminous intensity, observation distance has no impact on its value.
However, the apparent surface, i.e. the area perceptible to the observer, can vary according to the observer's position. The observer can see the entire apparent surface when facing the luminaire. If it is positioned next to the luminaire, this surface area decreases and so does the number of luminous fluxes.
Good to know: luminous intensity and luminous power are two quite distinct notions.
Luminous power and luminous intensity are two different notions that you shouldn't, either, confuse. Luminous power is expressed in Watts and represents the bulb's energy consumption. Moreover, this is the point of investing in LED bulbs like the LED 95 Milky distributed by Hoopzï. With a light output of 8W, it diffuses a luminous flux of 930 Lumens. With an incandescent bulb, a light output of 75W is required to achieve such luminosity, and 65W with a halogen bulb.
The different lamp technologies
On the market, you can find a wide choice of lamps that develop different characteristics. You should then know that there are several lamp technologies divided into 4 quite distinct categories.
Standard incandescent lamps
Invented in 1878, the standard incandescent lamp was the first lamp to use electrical energy to operate. Filled with inert gas, the bulb's glass body encompasses a tungsten filament.
While it offers very good color rendering, it has major drawbacks due to its uneconomical nature.
This model has a very limited lifespan compared with other lamp technologies, at 1,000 hours versus 2,000 hours for a halogen lamp. The incandescent bulb can quickly heat up and become scorching hot. So it can't be replaced straight away if it's burnt out. Wait until it has cooled down before handling.
The luminous efficacy of an incandescent lamp depends on several factors, including its state of wear and the mains voltage. In addition, it decreases over time.
Good to know: apart from decorative models, incandescent lamps no longer exist on the market. In application of a European directive, their import and manufacture have been prohibited since the beginning of 2013.
Halogen lamps (halogen incandescent lamps)
The halogen lamp also includes tungsten filament, but unlike the conventional incandescent model, the bulb does not contain gas alone. It includes inert gas and a halogen component.
Thanks to this halogen component, this type of lamp benefits frommore intense luminosity and a longer life than those of the conventional incandescent lamp.
The main drawback of the halogen lamp is its energy-hungry nature. Moreover, some models have been withdrawn from the market because they consume so much energy. However, it is possible to find halogen-type lamps developing a better energy performance.
Good to know: halogen tubes are not highly recommended for domestic use. Generally speaking, they are available in high wattages, i.e. over 100 W. However, such a high wattage is not essential for domestic use.
Compact fluorescent lamps
This type of lamp is an alternative to the classic incandescent bulb. It stands out above all for its good lighting capacity and low energy consumption.
This low-energy lamp is simply an improved version of the fluorescent tube to suit domestic use. It generally takes the form of a fluorescent tube folded on itself.
The compact fluorescent lamp comes in different models and can adopt the shape:
- A classic bulb,
- A tube bulb,
- A spiral bulb,
- From a globe bulb.
This type of lamp does, however, have certain shortcomings that you should not take lightly.
The fluorescent tube contains mercury vapors. In the event that the bulb breaks, you need to take a few precautions:
- Do not inhale the mercury vapour,
- Air-condition the room immediately to dissipate the vapor (minimum 10 minutes);
- Wear gloves before handling breakage to avoid cuts.
Different studies have revealed that compact fluorescent lamps emit a large quantity of electromagnetic waves. Nevertheless, these waves can be diffused within a maximum radius of 30 cm. To limit any possible health risks, you should avoid any exposure to these waves. These bulbs are not suitable for bedside lamps, and even less so for reading lights.
LED lamps
Unlike other lamp technologies, the LED lamp features an electronic device whose main role is to transform electricity into light. It is capable of producing light, even at very low voltage, while guaranteeing very good efficiency.
The main advantage of this type of lamp lies in its particularly remarkable progress. Indeed, manufacturers never cease to innovate their product to provide LED lamps that meet consumers' needs.
The special features of the LED lamp
LED lamp, a highly upgradeable luminaire
When it comes to light intensity, it's hard not to bring up the subject of the LED lamp. Appearing in 1962, the Light-Emitting Diode (LED) lamp stands out above all for its low-energy consumption. Originally, it was intended for the indicator lights of electronic devices and then for road and urban signage, before finally joining the list of equipment for domestic use.
LED lamps come in several types, depending on bulb wattage (W), color temperature (°K), luminous flux (Lumens), style... At Hoopzï, for example, you can find different models like theLED copper mirror head bulb (4W and 2,000°K) or theLED floating globe 200 lampshade bulb (8W and 2,200°K).
LED is an economical and environmentally-friendly lighting solution that is gradually replacing "classic" halogen or incandescent bulbs. However, it's important to remember that this solution is only effective if you choose a model suited to your needs and the room to be lit. To find out whether a bulb is right for you, check the indicators on its packaging. These represent the characteristics of the product in question.
What are the characteristics of an LED lamp?
Light output
The bulb's wattage reflects the lamp's energy consumption. For conventional bulbs, it can also be used to assess their luminous intensity. This unit of measurement can, however, mislead you in the context of the LED lamp, which is particularly energy-efficient.
In fact, the brightness of a 40-Watt incandescent bulb and that of a 3 to 5-Watt LED are roughly the same.
On product packaging, manufacturers often indicate the conventional bulb equivalent of the LED lamp in terms of wattage. For the LED 95 Clear chez Hoopzï, for example, it has a wattage of 7W equivalent to 60W for an incandescent bulb.
Luminous flux
If it's difficult to assess the brightness of an LED bulb with its wattage, you can refer to another quantity, i.e. luminous flux expressed in Lumens.
In this context, know that an LED bulb of 3 to 5 Watts can emit the same luminous flux as an incandescent bulb of around 40 Watts, i.e. between 300 and 500 Lumens.
The base
The base is the element that allows the bulb to connect to the socket. It comes in several models:
- The E27 base: this is a large screw-in model. The same type as the LED bulbs distributed by Hoopzï.
- The E14 base: this is a small screw-in model.
- The GU10 base: it has 2 studs that you can fix by performing a quarter turn.
- The GU5.3 or MR16 base: it is attached using its 2 studs.
The supply voltage
On the LED bulb's packaging, manufacturers indicate the supply voltage suitable for it. Some models can be connected to 12V direct current, others to 12V alternating current. There are also LED bulbs that operate on 230V alternating current.
It is formally recommended to respect the supply voltage indicated on the bulb's packaging. Otherwise, the bulb may burn out as soon as it is switched on.
The color temperature
This characteristic is a decisive element, because it defines the ambience generated by the light emitted by the bulb.
Expressed in Degrees Kelvin (°K), color temperature ranges from 2,000° K to 6,500° K. There are 4 shades of color that generate 4 different moods, :
- Very warm white: between 2,000° K and 2,200° K ;
- Warm white between: 2,200° K to 3,200° K ;
- Neutral white: between 3,200° K and 5,000° K (equivalent to the color of daylight) ;
- Intense white or cool white: over 5,000° K (not recommended for residential lighting).
Good to know: these data are provided for information only.
Particularly for bulbs distributed by Hoopzï, they generally vary between 2,000° K and 3,000° K.
The wavelength
The wavelength expresses the color of the LED lamp (red, green, yellow...). This implies that it does not concern white-lighting LED lamps.
The color rendering index (CRI)
This unit of measurement determines the LED bulb's ability to render the color of the surface and objects it illuminates. It refers to daylight and varies between 1 and 100. The ideal CRI is greater than or equal to 80.
This table summarizes some essential LED lamp features so you can get an idea of its main qualities.
| Caractéristiques | Valeurs |
| Light flux | 300 - 1,000 Lumens |
| Color rendering index (CRI) | 80 - 100 (reference is from 1 to 100) |
| Color temperature | 2,700°K - 6,000° (LED bulb can diffuse warm or cool light, depending on model) |
| Rendement lumineux | 30 to 100 Lumens/Watt |
| Classe énergétique | A+ (the bulb has a high energy performance) |
| Lifetime | 15,000 - 50,000 hours |
How to choose the right light intensity for a luminaire?
The choice of brightness for all rooms in the house shouldn't be left to chance. In fact, each of them is assigned to a specific function and its lighting requirements depend on this.
Then it's time to follow the professionals' recommendations regarding the amount of lighting needed for a room. To facilitate the calculation, they have taken into account the lamp's illuminance value, i.e., the amount of light received by the illuminated area.
Certainly, the data in this table remain indicative, nevertheless, they can be useful to you in choosing the amount of light needed in your interior.
| Piece to be illuminated | Quantity of light required per room |
| Between 100 and 300 Lux | |
| Living | Between 200 and 300 Lux |
| Between 100 and 300 Lux | |
| Between 100 and 300 Lux | |
| Between 200 and 500 Lux | |
| Bathroom | Between 200 and 500 Lux |
| Toilette | 100 Lux |
| Laundry room, garage, cellar... | Between 100 and 300 Lux, or even more depending on the activity carried out in the room |
| Hallways and entrance hall | 100 Lux maximum |
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Some rules about lighting
To ensure that a given area is well lit, it's essential to master these few rules.
To begin with, you need to determine the room to be lit. The light intensity and lighting power requirements of the bedroom are not the same as those of the living room, bathroom or kitchen. This enables you to define the area to be lit and to get a precise idea of the room's lighting requirements. In fact, the bedside table requires less light intensity than the kitchen worktop.
You must also consider the room's design style. The brightness of a dark-colored living room will not be the same as that of an all-white living room, even if the 2 rooms benefit from identical lighting.
The color of the light emitted by the luminaire acts considerably on your mood. It allows you to create an ambience tailored to your desires and the needs of the room. Know that warm light is conducive to relaxation, as it evokes tranquility as well as comfort. Cool light, on the other hand, is favorable for work areas, making you as dynamic as you are active.
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