Ian Stirling wrote:

Talking of light bulbs,
it seems extraordinary that they never say how much light they give out,
but only how much power they consume.

Look on the side of the packets.

There is often a number "1000 lumens" for example.
100lm/W is excellent, for the best fluorescants, 180lm/W is typically only
achievable with yellow sodium monochromatic low-pressure lights, 15lm/W or
so is fairly typical for your average tungsten light bulb, and CF lights
can be around 50-60lm/W.

Thanks very much,
I see that about half of my rather large store of light bulbs
have a lumen measure on them.

Tesco are just selling sets of 3 11 watt energy-saving bulbs very cheaply,
and these claim to give 600 lumen,
while a "soft tone" Phillips 60 watt bulb specifies 710 lumen,
which seems a little low by your measure.

Since I am in the presence of such luminous knowledge,
why does one never see very bright energy-saving bulbs -
I mean the equivalent of a 150 or 200 watt standard bulb?

--
Timothy Murphy
e-mail (80k only): tim /at/ birdsnest.maths.tcd.ie
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland