Measuring light intensity
Hi all,
again and again the measurement of light intensitiy is an issue. Usually you need a LUX meter.
There is an alternative:
Photographers used in the past hand held exposure meters. If you can get hold of such a meter use it. Ask older people. They often own such a vintage meter and are glad if it can still be of use. Usually these meteres measure the required exposure for an object. Most of them can measure alternatively the light source in terms of light units (EV). For the measurement you need to slide a calotte of milky tranparent material in front of the sensor. Range: -6 EV up to 16EV. (0.156 LUX up to 163840 LUX. The EVs you can directly convert into LUX. See Converion table 2 / last page
i.e. 3 EV => Liminance of 1 cd / m2 => Illuminance 20 LUX
An increment of Light units (EV) by 1 doubles the other values
Of course a LUX meter is much more comfortable in use but for small budget and reference measurement such a exposure meter is quite welcome.
But please take in account to measure from the same direction and from the same distance and omit reflected light from the environment (black surrounding preferred) in order to get comparable references. Same if you use real lux meters.
rgds John
Hi all,
again and again the measurement of light intensitiy is an issue. Usually you need a LUX meter.
There is an alternative:
Photographers used in the past hand held exposure meters. If you can get hold of such a meter use it. Ask older people. They often own such a vintage meter and are glad if it can still be of use. Usually these meteres measure the required exposure for an object. Most of them can measure alternatively the light source in terms of light units (EV). For the measurement you need to slide a calotte of milky tranparent material in front of the sensor. Range: -6 EV up to 16EV. (0.156 LUX up to 163840 LUX. The EVs you can directly convert into LUX. See Converion table 2 / last page
i.e. 3 EV => Liminance of 1 cd / m2 => Illuminance 20 LUX
An increment of Light units (EV) by 1 doubles the other values
Of course a LUX meter is much more comfortable in use but for small budget and reference measurement such a exposure meter is quite welcome.
But please take in account to measure from the same direction and from the same distance and omit reflected light from the environment (black surrounding preferred) in order to get comparable references. Same if you use real lux meters.
rgds John
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