lux / candela question

[lightnix]

I have a lamp which gives 400 lux at 0.5m and a client who wants to know what the output is in candela (cd).

Is there a way of working this out or inferring one from the other? Maths was never my strong point and from what I know the former is a measurement of light arriving at a surface, while the latter is a measurement of output.

All help appreciated.

[jtr1962]

100 candela. First you need to normalize the lux reading for 1 meter using the inverse square law, so you get 400*(0.5)²/1² = 100 lux. Lux at 1 meter equals candela.