Monday, 3 May 2010


In photometry illuminance is the total luminous flux incident on a surface, per unit area . It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance.In SI derived units, these are both measured in lux (lx) or lumens per square metre (cd·sr·m−2).
Both the illuminance and the lighting level are measured with the photometer. There are objects capable of producing their own light like the sun or the light bulbs: they are the light sources. Other objects reflect the light and direct it toward our eyes. This is the case of the house opposite my window: it looks like a chameleon. Framing is always the same, but the light is constantly evolving. And this is a basic lesson in photography: take advantage of the good lights.

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