Illuminance is the metric that is used to measure the light intensity within a space. It is measured in footcandles or lux — it is the amount of light lumens falling on a surface over any given square foot or square meter. Therefore, light intensity is measured in terms of lumens per square foot footcandles or lumens per square meter lux. Measuring the amount of light that falls on a surface allows us to evaluate if we have sufficient light to perform various visual tasks.
Lumens lm are the unit of measurement we use to quantify the amount of visible light the human eye can see. The luminous flux of a particular light source is measured in lumens. You many have noticed when you buy light bulbs for your house that they indicate lumen output. Now, lumens are simply a unit of light, but when put into context over a given surface area, they become especially a more useful metric. Lux is simply the unit of measure used to describe the number of lumens falling on a square foot footcandles or square meter lux of a surface.
But what if we spread this over 10x the area i. Well, the illuminance or lux would decrease to a less intense and dimmer lux. We use the same approach for footcandles, only our units are lumens per square foot. Now, you might be thinking we already covered lux, so why add in this metric? Different people use different metrics and for different reasons.
Simply put, where 1 lux equals 1 lumen in a square meter, 1 footcandle equals one lumen per square foot. Luminous flux is how to measure the perceived power or total amount of light output from a light source. When the number of lumens — the unit-amount of visible light a human eye can see, is used to measure the intensity of a light source. A one-meter sq. T here are several types of lighting metrics and measurements used in the lighting industry.
While these are useful to lighting experts, how do these terms relate to the real world? We need a little context. A typical classroom, for example, is recommended to have a light level of around footcandles or lux. Compare this to a professional laboratory which the lighting standards recommend have a light level of footcandles or lux. The recommendations are based on years of visual testing to determine how much light the human eye needs to properly see different tasks with varying levels of detail.
This worked better in the past as most lights were incandescent and the variation in efficiency between different manufacturers was small. Nowadays with more energy efficient lights, watts are not such a useful way to consider brightness. A watt is actually a unit of power, or the rate of energy used or generated over time. Energy companies use watts to track the amount of electricity we use in Kilowatts per hour kWh , which is 1, watts of power over one hour of use.
So if we have a w lightbulb switched on for 1 hour, this would be 0. In basic terms, Lumens lm are a measure of how much visible light is emitted by a light source, this is described technically as its luminous flux. The total power of the visible light is represented by the total number of lumens given off.
Bright sunshine is about 50, lux. Home — How Is Brightness Measured? How Is Brightness Measured? See all comments There are a few factors that affect how bright a bulb is: Firstly, it depends on how much light it produces. With energy efficient bulbs such as LED this is somewhat different because there is no hard and fast rule to correlate wattage with output, and LEDs use much less power.
One brand's 9 Watt LED bulb may emit enough Lumens to replace a 60 Watt incandescent, but another brand may need to use a less efficient LED such as 12 Watts to create enough lumens to replace that same 60 Watt bulb.
Because of this it is much more important to look at lumens than watts when considering light output. If you have any questions or would like to discuss your lighting needs, please feel free to request a free consultation online.
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