The lumens and candlepower are similar measurements, but there are some differences between the two. Lumens measure the amount of light produced while candle power measures the amount of energy used to produce it.
Candlepower is equal to a measurement of the luminous flux generated per unit of fuel burned, and it is measured in units called candelas. One candela is equivalent to the luminous intensity of a single candle placed 10 feet away from you. To calculate the number of candelas required to generate a certain amount of lumens, multiply the lumens value by 10. For example, a 1000-lumen bulb produces about 10 candelas of light.
Candlepower is measured in watts. One watt is defined as the power needed to raise the temperature of one gram of water by one degree Celsius. To convert watts into lumens, divide the wattage by 4.2. In our example above, we’d divide 1000 by 4.2, which equals 212 lumens.
The lux unit is used to describe the brightness of light sources. It's based on the human eye's perception of brightness.
One lux unit is equal to the amount of light produced by a candle burning at a distance of one meter. So, if you're measuring the brightness of a light bulb, you'd divide the lumens rating by four to find out how many lux units it produces.
There are two ways to measure the brightness of the light. You can use either lux or footcandles. Footcandles are a measurement of the amount of light falling on a specific area.
They're usually expressed in terms of illuminance, which is the total amount of light falling on an area over some time. For example, a reading of 10 footcandles indicates that the light source provides enough illumination to read comfortably under normal conditions.
To convert between lux and footcandles, multiply the number of lx by four.
The radiant flux of a source is the total amount of electromagnetic radiation it emits. These include infrared, ultraviolet, X–ray, radiation, microwave, etc., as well as visible-range wavelengths of electromagnetic energy (luminous power). Examples include infrared, which ranges from 700 nm to 1
Lumen measures light intensity, while lux measures brightness. One measure of a candle is its candela rating, which is determined by the total number of candles needed to produce 1 lumen of illumination at 1 meter away. Candelas are used to determine the brightness of candlelight.
A lux unit of measurement is equal to the lumen output divided by the area illuminated. Candlepower is another term for lux. So, one candle gives off 100 candlelight units and thus has a power of 100 candles.
For a point source, the brightness decreases with the square of the radius. This is because the amount of energy emitted per unit area increases linearly with the size of the emitting surface.
However, for a nonpoint source, such as a lamp, the brightness decreases exponentially with the distance from the source. Why? Because the total amount of energy emitted over the entire surface of the source decreases with the cube of the distance.
The inverse-square law does NOT apply to all situations. It doesn't even work in most cases. A good example is a flashlight. If you shine a flashlight into a dark room, the beam gets brighter as you move away from the light source.
The lux measurement procedure consists of three steps:
1. Calibrate the instrument
2. Determine the type of light source
3. Calculate the lux value
To calibrate the instrument, it must be placed on a flat surface where there is no ambient light. If the room is well-lit, place the instrument inside a black box.
Lumens measure the total amount of visible white light emitted by a source. Candles are measured in candlepower. In the United States, one candela is defined as the luminous flux emanating from a surface of one square centimeter of the area under standard illuminant conditions.
To calculate lumens, multiply the number of candles by 0.01. So, if you wanted to know how many lumens a 60-watt incandescent bulb produces, you could do the following calculation:
60 x.01 6 lumens
You can use this same formula to find out how much illumination a 40-watt LED bulb provides.
For example, if you want to know how many lumens an 80-watt halogen bulb emits, you could do the calculation:
80 x.01 8 lumens
A lumen rating describes how much light it emits in every direction, while the candela rating describes the max amount of light that can focus into one spot. To make sure you're comparing apples to apples, you want to know the ratio of lumens per candela. This will help you determine whether you're getting enough light for your dollar.
Lumens are a unit of luminous flux, while candles are used to describe the brightness of a source of illumination. A lumen is defined as one lumen per square meter per second, and a candela is defined as one candela per steradian per second.
To convert candles into lumens, divide by four pis (4*pi). For example, a 60-watt bulb emits about 10,000 lumens per hour. This translates to 2.5 million lumens per day. A lumen is equivalent to a candela divided by 12.57. So, a 60-watt bulb is equivalent to 3.7 candelas.
Lamps are one of those things you probably don't think about much unless it's something you're trying to do. But there are some important differences between lamps and bulbs.
For example, most lamps have a fixed amount of lumens, while most bulbs have a variable amount of lumens.
A watt measures how much electricity is used by a device, while a lumen measures the amount of light produced. To convert lumens into Watts, multiply the number of Lumens by 0.0126.
For example, if a bulb emits 1000 lumens, it consumes 10.6 watts. This formula applies to incandescent bulbs, fluorescent tubes, and compact fluorescent lights.
