"Dave Plowman" wrote in message
...
In article ,
The Natural Philosopher wrote:
Average lightbulb is around 1-2%.efficient. Halogen being at the upper
end, and cheapo dim long lifers at the other.

However the eye perceives brightness logarithmically. To be twice as
brght probably means 4-10 times the power. That makes efficiencty
variations of even 2:1 pretty insignifiocant.

I recently changed the bulbs in my car headlights. Same size. The
difference in light output was *dramatic*.

I couldn't give a toss about the theory, but the practice means a great
deal.


That's because the old ones are shagged due to the vaporized metal from the
filament blackening the inside of the glass envelope. I am assuming they are
not halogen (or gas discharge for that matter) which do not suffer such a
loss of output with ageing.

Dave

"If you don't know where you are going, any road will take you there"