This means that it is a very good light output measure as it is adjusted to take into account the different sensitivity the human eye has to different wavelengths. This is a straight forward measurement of the light intensity as perceived by the human eye. The simplest and arguably the best standard measurement of light output is the lumens measure. Obviously the cover will absorb some light a and as a consequence the brightness will be reduced. This is because the global bulb is manufactured by producing a spiral CFL and then putting a glass global cover on it to give the aesthetic design character. With traditional bulbs a clear bulb would produce more light than a pearl one and in a similar way, with modern CFL light bulbs a 15watt globe will produce less light output than a 15 watt spiral CFL. As an example a 60watt incandescent bulb will produce the same light output as a 15watt CFL but it may only require a 40 watt halogen bulb or a 10watt LED to produce the same light level in a room! The other complexity is the light bulb cover. Clearly we now need to understand light output in more detail and use more sophisticated light measurement techniques now that we have a spectrum of different light bulb technologies. Now this is all well and good when you only have just one technology, but the plot thickened with the emergence of the fluorescent tube because an 18watt fluorescent tube produced far more light output than a 100 watt incandescent light bulb. In fact, it almost turned into the universal measure nearly achieving the level of accreditation that a British Standard would! Importantly, wattage is not a measurement of light output it is a measurement of power consumption, but as all light bulbs used the same technology this measure proved to be a good brightness indicator. So people would say, ‘this room needs a 60watt bulb’ or ‘this room needs a 100watt bulb’. People just used to use the light bulb wattage as the brightness measure. When we just had incandescent light bulbs, getting a good indication of the brightness of the bulbs was quite straight forward.
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