Sanjay's Lighting Articals [Archive] - Canreef Aquatics Bulletin Board

StirCrazy

12-28-2007, 05:46 AM

PPFD is photosynthetic photon flux density, it is an average value over an area in a specific wave lenght for a fixed amount of time.. here is a definition.

Not energy but unit expressed at the number of the light quantum ( photon ) which is a particle of the light are photosynthesis light quantum flux density. The photosynthesis is influenced according to the number of the light quantum which is emitted to the chlorophyll. Generally, it the light quantum of the 8-10 piece in order to consume carbon dioxide ( carbon dioxide, CO2 ) of the monad of the photosynthesis. Then, it is photosynthesis light quantum flux density to show the number in which the light quantum at 700nm wavelength from 400nm which is the chlorophylloid absorption wave length area was emitted at unit time and per unit area. Energetic, the wavelength shortly and proportionally rise on the energy of ( the frequency is high ), because there is the relation of e=hn ( e : Energy h : Constant n : Frequency ). The unit is umol m-2s-1. 1 mol shows 6.02~1023.

CCT is correlated color temperature, because floressent tubes contain a bunch of different elements to creat a color they do not emit an exact black body color like incadesent lights do. but they come close to it so they designed a different way of aproximating the color and this is expressed as CCT so if you have a bulb that has a CCT of 13000Kelvin it would apear simular to a incadesent's black body temp even though they are not the same color.

Steve

fkshiu

12-28-2007, 06:39 AM

This is my totally lay and oversimplified understanding of PPFD and CCT, but it fulfills my rather selfish needs:

PPFD: Another way of measuring PAR - i.e. the higher the better.

CCT: What the actual colour temp of the bulb is (as opposed to what the manufacturer labels it as) - i.e. CCT of 14,000 on a "20K" bulb means that it actually appears white as opposed to the advertised blue.