Lumens is a measure of light flux, so is independent of the area. It is essentially the amount of light available. So think of a bright light. It has a fixed amount of lumens, regardless of how near or far you are.
Lux is the light level at a surface. If you think of a light bulb, the lux will vary with the distance from the light source because the light spreads out.
1 lux = 1 lumen per sq meter.
Most light meters read out in lux, which is a measure of the brightness at a surface. You will measure more luxes when you are closer to the bulb, than when farther away.
Suppose you are measuring a compact flourescent lightbulb (CFL), which is roughly cylindrical in shape. You use your light meter and read 1000 foot-candles at about 1/2" from the lightbulb. How do you compute the lumens of the lightbulb?
(1) Convert the foot-candles to lux:
1000 foot-candles = 10764 lux
(2) Compute the area over which that lux value applies. This is roughly a cylinder that is 1/2 inch bigger in all directions from the bulb. So measure the bulb. We are going to convert all of our measurements into metric units. 1/2 inch = 0.0127 meters
bulb height = 9 cm or 0.09 m
bulb radius = 2 cm or 0.02 m
inflated height = h = 0.09 m + 2 * 0.0127 m = 0.1154 m
inflated radius = r = 0.02 m + 0.0127 m = 0.0327 m
area_of_cylinder = 2*pi*r*(r+h) = 2 * 3.14 * 0.0327 *(0.0327 + 0.1154) = 0.03 m^2
(3) Compute the total lumens of the bulb:
bulb_lumens = 10764 lux * 0.03 m^2 = 327.5 lumens.
Notes:
a) If your bulb is more like a sphere, you should use the formula for the surface area of a sphere rather than a cylinder.
b) When measuring the lux or foot-candles of the bulb, you should measure at several locations and average the number.
c) If you measure from a large distance away from the bulb, then you can ignore the size of the bulb in your calculations.
Brightness is measured in lumens so the bulb has a brightness of 100 lumens. The electrical power the bulb uses is measured in watts. The efficiency of a bulb is expressed in the number of lumens produced per watt of electric power.
The unit for intensity of light is candela(cd). However, bulbs are rated by their power usage which is measured in watts(W)
Bulb brightness is measured in lumens which express the amount of light produced, while the electric power used is measured in watts. The typical efficiency of some different types of bulb is: Incandescent 12 lumens per watt Halogen 17 lumens per watt CFL (compact fluorescent) 50-60 lumens/watt LED (light-emitting diodes) 90-100 lumens/watt.
There is no direct conversion between lumens and watts for LEDs since they are measured differently. However, as a rough estimate, a 60-watt incandescent bulb produces about 800 lumens. For an equivalent LED output, you would typically need an LED bulb with around 800 lumens.
If you have the wattage of the laser you can plug it into a formula X/P=L. Where One lumen is equal to 0.001496 watts (1.496mW) which is Power. X is the number of watts or milliwatt and L is Lumens. So if you have a 1 watt laser you have 668.449 lumens being produced by it.
Brightness of light sources is measured using a unit called lumens. Lumens indicate the total amount of visible light emitted by a source, with higher lumens corresponding to greater brightness.
The brightness of light bulbs is typically measured in lumens. Wattage can also be used as a general indicator of brightness, but lumens provide a more accurate measurement of the actual amount of light produced by a bulb.
The amount of power they consume is measured in watts. The amount of light they put out is measured in lumens.
Brightness is measured in lumens so the bulb has a brightness of 100 lumens. The electrical power the bulb uses is measured in watts. The efficiency of a bulb is expressed in the number of lumens produced per watt of electric power.
usually lights are measured in lumens
Currently maximum LED luminous efficiency is about 114 lumens/W, measured at 50mA. Average luminous efficiency is about 104 lumens/W. Ordinary LED light effect is about 60 lumens / W. 18W is about 130 lumens is about 1080 lumens.
The unit for intensity of light is candela(cd). However, bulbs are rated by their power usage which is measured in watts(W)
Luminous flux is measured in lumens (symbol: lm).
The relationship between brightness and perception in lighting, measured in lumens, demonstrates a logarithmic scale because our perception of brightness increases more slowly as the actual brightness increases. This means that doubling the lumens doesn't result in a perceived doubling of brightness.
Light intensities are usually measured in candle power. What that means is the equivalent of the light of one candle, measured at a distance of one foot, sometimes called, `foot candles' or `candellas'. +++ In the SI system the flux or "amount" of light, is measured in lumen; and the illuminence or brightness of the light, on a surface in lumens per square metre, a compound unit called the lux.
Bulb brightness is measured in lumens which express the amount of light produced, while the electric power used is measured in watts. The typical efficiency of some different types of bulb is: Incandescent 12 lumens per watt Halogen 17 lumens per watt CFL (compact fluorescent) 50-60 lumens/watt LED (light-emitting diodes) 90-100 lumens/watt.
It isn’t. Light is measured in lumens. Electric is measured in watts or kilowatts.