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Re: comment on lumens

> Assuming you have the same ballast and are
> comparing two lamps with the same wattage rating, the light energy that
> leaves the system has to be equal for both lamps, right?

Sorry, no, that's not right.

The bulb is coated with a fluorescent material which converts the UV
radiation emitted by the electric discharge into visible light. This
conversion process is lossy, some amount of the UV radiation is converted
into heat. The efficiency of this process is varying with different kind of
fluorescent materials.

So the light energy leaving the system has not to be equal for different
kind of lamps, because more or less UV energy is lost as heat, dependent on
the efficiency of the flourescent substance.