On Sun, 22 Oct 2017 09:35:25 +0100, "Dave Plowman (News)"
wrote:

In article ,
John Rumm wrote:
On 21/10/2017 22:10, NY wrote:

Also, can you get an LED bulb yet that is as bright as a 25 W CFL which
is I think is equivalent to about 150 W tungsten?

I have seen some 11W ones that claim to match a 100W tungsten...

It's interesting to use one in a common situation - say a central pendant
fitting in a white or light coloured room, and compare the ambient light
between them. My guess is they have a very special tungsten 100w they used
for comparison.

I've heard that the claimed lumen output from LED bulbs is often
overstated.

Apparently there is an acceptable tolerance in stated lumens to
account for the variation inherent in tungsten bulb manufacture. But
LED bulbs can be manufactured to a more precise light output, so
manufacturers can claim a higher lumen value while ensuring that the
bulbs will fall within the acceptable range.

I've also heard that some claims used to be based on the output from
the LED chip rather than the entire bulb. I'm not sure if this still
goes on, or whether it's been banned.