Seed Swaps

Evaluating CFL Bulbs - Spectral Curves

26 Feb 2012
Cloudy 2°C / 36°F

I finally got over to my old shop early this morning and ran some curves on the spectrophotometer. I ran curves on Natural Daylight bulbs and on Soft White bulbs. I was pretty surprised by the results. I tested 23W bulbs. I scanned the graphs and overlaid each over the PAR curve (Plant Active Response) or the light wavelengths and intensities that plants need. The CFL curves were very similar to standard Daylight and Soft White florescent tubes. Last year I ran a curve on a florescent growlight, and it turned out to be almost identical to a composite of the two CFL’s, with wavelengths in both ranges.

It was very obvious that the Natural Bright White CFL bulb was a very close fit to the Plants PAR for Plant Growth. Although a plant needs a full spectrum, the amount of light required in each of the wavelengths vary based on the stage of plant development. Seedlings an pre-blossoming plants require large amounts of light in the wavelengths between 400nm and 550nm. Once the plant starts to blossom, the light absorption shifts drastically to the 550 to 700nm range.

My conclusion was clear. If I am not going to blossom plants under artificial light, then I don’t need a grow light, or a Soft White bulb. I sort of knew this before my test, but this certainly validated it. I’ll repost this in General Chit Chat. I doing a journal entry to keep all my experimental lighting test results in my Experimental Lighting Garden.




Thanks for sharing this.

Posted on 26 Feb 12 (almost 4 years ago)

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