Does a higher K Number On A Fluorescent Tube Mean That It Is Brighter?

General Technical Stuff April 20th, 2009

One Response to “Does a higher K Number On A Fluorescent Tube Mean That It Is Brighter?”

1. Daniel Says:
   April 20th, 2009 at 11:19 pm

   Hi Peter and Anne

   Many thanks for your interesting question

   The colour (or kelvin K rating of fluorescent tubes) always brings up interesting conversations in the lighting community

   The cool white globe usually produces the most light out of all the colours

   Eg an Osram 35W T5 cool white tube produces 3350 lumens whilst the same fluorescent tube in a daylight colour only produces 3050 lumens

   A 5000K or 6500K globe would appear brighter but as you can see from above it actually produces less light. The reason it gets dimmer is because the lamp manufacturers need to put more phosphor in the tubes to make the colour whiter which means less UV radiation (light) gets out which means you get a dimmer light

   Now you are probably asking what these K numbers actually mean then. Basically the higher the number – the whiter the globe. A warm white globe (2700K) will appear quite yellow when you put it next to a daylight globe (6500K). the daylight globe is meant to represent daylight at midday at some place in the world where they decided the standard for a daylight coloured fluorescent tube.

   Today though there is still no machine that decipher colour temperatures of fluorescent lights so the lighting manufacturers use a panel of people and average out the panels response when labelling their products

   But to answer your question if you need more light output, you may need to change the light fitting as you wont get any more light just by changing the colour of the lamp.

   I hope this all makes a little more sense now.

   Kind regards

   Daniel

   Hope this makes sense

   Kind regards

   Daniel

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