Actinic vs. 20000k

[RegalFlush17]

Does anyone know what the difference is between actinic lights and a bulb with a color temp. of 20000k. They both are in the blue spectrum of light. Is the difference that actinics provide no usable PAR while the 20000k bulb does? Thanks

[Doc Shake]

actinics are higher PAR than the 20000k. a 20000k just gives more of a daylight look than actinics alone.

[MrAnderson]

Actinics provide PAR.

 

PAR stands for photosynthetically active radiation. Since chlorophyll a's absorption peak is around 420nm (purple actinic emission wavelength) and chlorophyll b's absorption peak is around 460nm (blue actinic), these definitely qualify as photosynthetically active wavelengths.

 

The difference is that actinic bulbs provide a very narrow range of emitted wavelengths. If you look at a spectrograph, the peaks are very narrow and sharp, peaking at either 420nm (ex: Coralife's actinic 03) or 460nm (ex: SunPaq actinic 460). This is SunPaq's actinic460 emission graph:

 

 

A 20K bulb also has it's peak in the blue range, but has a much wider range of emitted wavelengths. Although you can't see them because the predominant emission is blue, there may also be red, yellow, green, etc. 20K, 10K and 6700K all have their peaks in the blue range, but because of varying contributions by other emitted wavelengths the light looks more white or yellow. I'm showing a 10K bulb emission graph for comparison (can't find 20K):