How are Lumens measured?

[amtrakuk]

Perhaps an odd question or stupid but yet again I've tried another 2700k 9 watt LED lamp what claims to be a 60 watt equivalent to coin a phrase from Nigel - "Well I'm sorry" but there is no comparison I'd say its more a 40 watt equivalent and again all the colours are washed out.

It got me thinking, how do they measure the source lumen output and are they as efficient as their made out? I'll explain.

Take an 8 watt LED chip, the light from the chip generally speaking shines in one direction and if you point the light meter at the 8 watt LED chip it will measure X lumens - but that is on one direction! But when the optics sat on top of the LED chip have spread the light around 360 degrees it will naturally be dimmer.

In comparison take an 8 watt Fluro tube. If you point the same light meter again at the tube it will show less lumens because the source light generated is surrounding the tube not just from a single point in one direction like the LED chip.

Sure someone has covered this but every LED I have tried be it Filament, COB or Corn Cob has yes generated light but no where near the quality of an inky!