The lux (symbol: lx) is the SI derived unit of Illuminance and luminous emittance, measuring luminous flux per unit area.[1] It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception.
Lumens :
The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source per unit of time. Luminous flux differs from power (radiant flux) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to various wavelengths. Lumens are related to lux in that one lux is one lumen per square meter.
The lumen is defined in relation to the candela as
1 lm = 1 cd ⋅ sr.
A full sphere has a solid angle of 4π steradians,[1] so a light source that uniformly radiates one candela in all directions has a total luminous flux of 1 cd × 4π sr = 4π cd⋅sr ≈ 12.57 lumens.[2]
Beam Distance ( Measured as per ANSI FL1 Standard )
Beam Distance is the Distance travelled by the beam with a minimum Visibility of 0.25 Lux (Moon Light) at the end of the Beam
Some Flash Lights that are Imported usually have altered or fake distance in their Specification.
Schaff Displays only true Specifications on Our Flash Lights. Our Flash Lights are Checked as Per ANSI Standard
Finding the true range/distance capability of your long range flashlights. Using a digital light meter, Digital lux meter, or lux meter app/ light meter app on your phone.
You will need.
1. A lux meter or phone with a light meter app
2. Tape measure
3. Calculator
4. A flashlight for which you wish to measure range
Make sure that the distance your using is far enough away that the flashlight beam is fully converged. This makes a particular difference if your using a light with an aspherical lens. The beam will have a cross over point as show above. This is less critical with reflector based lights as there is not the same cross over, however falsely high readings can still be made if your too close.
Place Your Flashlight on a Tripod or Holding Device.
Measure a distance of 1 Meters from a Wall or a White Board and Place the Holding Device 1 Meter away from a wall or a White Board
Power the light on
It will be easier to measure if you have the light in a stationary position and move the meter rather than the other way around.
Move the sensor around on the wall till you find the brightest spot. This will give a better result than using the peek hold function and moving the flashlight around.
Measure the Lux (surface Light Intensity)
Formula to measure the Distance of the Beam is :
Use the Inverse Square Law to calculate the beam distance to 0.25 lux as follows:
Surface light intensity x (distance)2 = peak beam intensity
where:
√( peak beam intensity /0.25) = Max Beam Distance
Surface light intensity is in lux (lx)
Distance and Max Beam Distance are in meters (m)
Peak beam intensity is in Candela (cd)
For Example :
Let Surface light intensity in Lux = 35000 Lux
Distance Measured = 1 Meter
peak beam intensity = Surface light intensity x (distance)2
peak beam intensity = 35000 x (1)2
Maximum Beam Distance = √( 35000/0.25) = 374.16 Meters
