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This may not be all about how it works, but some background is good too.
A lux meter is a device for measuring brightness, specifically, the intensity with which the brightness appears to the human eye. This is different than measurements of the actual light energy produced by or reflected from an object or light source. The lux is a unit of measurement of brightness, or more accurately, illuminance. It ultimately derives from thecandela, the standard unit of measurement for the power of light. A candela is a fixed amount, roughly equivalent to the brightness of one candle.
While the candela is a unit of energy, it has an equivalent unit known as thelumen, which measures the same light in terms of its perception by the human eye. One lumen is equivalent to the light produced in one direction from a light source rated at one candela. The lux takes into account the surface area over which this light is spread, which affects how bright it appears. One lux equals one lumen of light spread across a surface one square meter.
A lux meter works by using a photo cell to capture light. The meter then converts this light to an electrical current, and measuring this current allows the device to calculate the lux value of the light it captured.
The most common use of this type of meter is in Photography and video filming. By measuring the light in luxes, photographers can adjust their shutter speed and depth of field to get the best picture quality. The device can also be very useful for filming outdoor scenes of television programs or movies as it allows adjustments to make sure scenes filmed in different light levels have a consistent brightness on screen.
To a very limited extent, it is possible to use a camera as a makeshift lux meter. This works because some cameras measure light and automatically adjust the exposure time appropriately. Using a formula, a photographer can then reverse the calculation and convert the stated exposure time into light levels. This method has several limitations, including the fact that some light is absorbed as it passes through the camera lens, so the calculation must be adjusted accordingly. The method can be useful in situations where a separate meter is impractical, however, such as with delicate objects in a museum that can’t easily be reached without disruption.
Another common use of a lux meter is in meeting health and safety regulations. It can be used to check whether a room is bright enough to meet any rules designed to protect workers from suffering damage to their eyesight, for example. The meter takes into account the size of the room in a way that simply measuring the intensity of the light source in lumens would not.
Sources: wisegeek
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What do you use to measure light?
there is an instrument called lux meter. i believe that it works with a complex electronics circuitry using light sensitive devices. it directly gives the reading in lux.
What does LUX stand for?
The lux is the SI unit of illuminance, and is equal to 1 lumen per square meter.
Instrument used by umpire in cricket to measure light intensity?
lux meter or light meter
How do you calculate a lux level in a room?
To calculate lux level in a room, you need to measure the illuminance using a lux meter. The lux meter records the amount of light falling on a surface per unit area. By taking measurements at different points in the room and averaging them, you can determine the overall lux level.
What would you use to measure the brightness of a light bulb?
You can use a light meter to measure the brightness of a light bulb. This device measures the illuminance or luminance level produced by the light bulb and gives you a numerical value for its brightness in units such as lux or foot-candles.
How many lux is a 250w halogen bulb?
A 250W halogen bulb typically produces around 5000-6000 lux at a distance of 1 meter. Lux is a measure of illuminance, or the amount of light falling on a surface.
How many lux are there in an area of 25 square meter?
On a very dark night, nearly none.
How do you measure light under room conditions?
Light in rooms can be measured using a lux meter, which quantifies the intensity of light in lux units. Lux meters are portable devices that can provide an accurate measure of the light levels in a room, helping to ensure proper lighting for various activities and tasks.
Who invented the lux meter?
Lux meter is a term sometimes used to refer to a light meter. If you mean who invented the light meter, Weston marketed the first photographic selenium meter in 1932, which was not well received. Dr. Bruno Lange is also credited with inventing a much more practical version in 1933 and started a company that year. I believe both of these versions were exposure meters and not designed to simply measure illumination. The meter has gone through various improvements for which patents have been granted for, thus there is more than one inventor of a light meter (Joseph Hostetter applied for a patent for a type of light meter in 1974). Lux is the metric version of the Imperial measurement called foot candle, which is based on the level of visible light at a point that is one foot away from one candle and spread out over one square foot. Although lux was a known quantity much earlier than the invention of the meter, would not be until the use of modern materials made light measurement possible using electronic means.
How many candelas equals 1 lux?
They really aren't equal because they measure two different things. However, they are related to each other.The Candela is the measure of the luminous intensity of a light source. A higher Candela number means a brighter light. Lux is a measurement of light density and means lumens per square meter. Again, a greater number of lux means that the surface being illuminated by the light is is receiving more light per square meter.The formula for calculating the conversion of candelas to lux is E = I/(D*D) where E is the Illuminance of the the surface in lumens per square meter (lux), I is the Intensity of the the light source in Candelas and of course (D*D) is the square of the distance from the light source in meters.Therefore 1 Candela will illuminate a surface with 1 Lux only at one meter from a light source. At different distances it will illuminate to different densities of light.For example: Solving for E, that same one candela light source would only read 1/4 lux at two meters [ 1/(2*2)] and 1/16 lux at four meters [1/(4*4)].If you know the lux at a given distance in meters from the light source you can solve for I and it will give you the intensity of the light in Candelas. From that you can calculate the intensity of the light.For example: Solving for I, multiply the lux times the square of the distance in meters and you will have the intensity of the light source in Candelas.So a reading of 8 lux at a distance of 3 meters would mean that the light source has an intensity of 8*3*3 or 72 candelas.
What object could you use to measure the brightness of the bulb?
An item called a LUX meter is usually used for the determination of the brightness of a light bulb. It is generally a meter that measures the amount of incident white light.
How would you measure the brightness of light being produced by a source?
The brightness of light produced by a source can be measured using a device called a photometer or lux meter. These tools measure the illuminance of light in lux, which is a unit of measurement for the amount of light that reaches a surface. By placing the photometer at the location where the light is being emitted, you can quantify the brightness level.
