I’ve heard plenty of different discussions where growers or sellers talk about different kinds of crop lighting.
I’ve heard why Lumens or Lux are better units for measuring light intensity than Footcandles-I’ve also heard that PAR is the best reading because it’s not just taking into account one light wavelength, and the whole spectrum that plants need to grow.
Is that what I should be following when comparing lamps and different types of grow lights-should I always use PAR?
P.A.R. (Photosynthetically Active Radiation) is a good measurement to use for grow lighting, but it’s not necessarily “perfect”-so it should be taken with a grain of salt when people talk about PAR readings in comparing how crop lighting performs. Lumens or Lux measures the “brightness” of light in the green bandwidth of light-the one plants don’t actually use much of-that’s about 555 Nanometers, technically speaking. Because HPS and MH lamps can only change their “cake mix” so much inside with various percentages of metals, salts, etc that create the “color” of the light, it’s not a bad measurement when comparing HPS to HPS or MH to MH-you just can’t use it to compare say, a MH lamp to an HPS lamp. With a PAR reading you COULD compare a MH reading to an HPS reading, because PAR measures a wider rainbow-and in what is present day knowledge of the ratios of colors of light , like red, blue, orange, etc that plants need to grow. But it can still lie. PAR readings will tell you a MH will is producing more PAR lighting, while slightly less intense when compared to on a Lux or Lumens Meter-so you move the MH light source closer.
So, by all accounts the MH lamp should yield more, right?
Truth is, it rarely does! Why? Because it’s silly to think that artificial light behaves like natural light (color aside; behavior, folks) and it’s even sillier to think that all plants want the same ratios of light at the same time all of the time too. That’s not how it works in nature, so temper science with some practical working knowledge is the advice here.
[quote]Heres’ an Example: a 400 watt metal halide lamp provides about 140 watts of PAR. A 400 watt HPS lamps has less PAR, typically 120 to 128 watts Wanna Know More About Something in Your Growroom? drop a line-get answered[/quote]
[youtube width=”560″ height=”315″ video_id=”dJJt5Vykxqs”]
Above: Crop Lighting levels are tested at 1:24 in the video.