Chart demonstrating slow startup for new light bulbs

Thanks to Ed Thurstan for the results of his neat experiment comparing the light up time of the new-fangled fluoro bulbs compared to the perfectly OK old incandescent bulbs that we now can not buy.

As Ed says:

My 75W incandescent bedside lamp bulb finally failed. So I installed a Philips 18W “Ambiance” fluoro, which is claimed to be equivalent to 100W Incandescent bulb. It emitted a dull glow befitting a mood light in a funeral parlour.

After waiting several minutes for sufficient light to see what I was doing, I set up an experiment with a digital camera to measure the light intensity from the fluoro, and compare it with ancient 60 and 75W incandescent bulbs still working around the house.

I set the camera on a tripod, aimed at a spot illuminated by the lamp. I set the camera to take a shot every 15 seconds, with the aperture and ISO fixed but the shutter speed allowed to vary to maintain a constant exposure.

Then I ran each of the three bulbs through a trial to see how long each took to achieve their maximum intensity from when the lamp was switched on. So the shutter speeds give a direct measure of light intensity.

Finally I normalised the results relative to the maximum intensity of the fluoro being treated as 1.

4 comments to Chart demonstrating slow startup for new light bulbs

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  • Siliggy

    My children found a simple way to solve this problem. In the bathroom they turn on the heat lamps instead!

  • Bob in Castlemaine

    Ed’s experiment confirms my scepticism about the line pushed by the promoters of CFLs that they take only a few seconds to reach full light output. From my experience they are certainly almost useless in applications where instant light is required.

    Also it would seem that CFLs can be dangerous.

  • Graeme Inkster

    My experience is that they vary in response.
    I have one CFL in parallel with an old incandescent with the latter coming on first. The second (CFL) comes on in about 5 seconds, and builds up in intensity fairly rapidly.
    The other area is lit (?) by 3 CFL lamps (in the same fitting), which conform more to the above. It is possible to see these CFL’s change individually if they are from different manufacturers. I have never timed it for light build-up but I would not dispute that 8 minute timing.

    But these CFL’s are expensive, and their shelf life is far poorer than stated. Factor in the mercury and its another green mistake.

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