In this article we’ll examine a video comparing HID and LED grow lights with a spectroradiometer, a device that can measure the amount of light emitted in each particular color range. This is important because most of the light produced by HID bulbs is not used by plants.

A standard light meter will read in lux or lumens, which measures the amount of light across the visual range of the spectrum. By examining the readings from the spectroradiometer, we can see how much light is emitted by a 330 watt LED grow light, a 400 watt metal halide and a 600 watt HPS, that the plants can actually use. Let’s take a look at the video…

• Brief explanation of the test [0:40 mark]
• 330 watt Lumigrow LED test, 32″ from LED [1:00 mark]

• LED Test Readings, 330w —  Bin 1 = 0.23, Bin 2 = 26.59, Bin 3 = 169.1, Bin 4 = 12.04, Bin 5 = 0.79

• 400 watt Metal Halide test, 32″ from bulb [2:25 mark]

• MH  Test Readings, 400w —  Bin 1 = 9.97, Bin 2 = 11.18, Bin 3 = 28.20, Bin 4 = 17.04, Bin 5 = 40.22

• 600 watt High Pressure Sodium test, 32″ from bulb [5:02 mark]

• HPS Test Readings, 600w — Bin 1 = 0.79, Bin 2 = 10.80, Bin 3 = 87.48, Bin 4 = 12.11, Bin 5 = 41.30

• Short interview with George Chan from Lumigrow about grower reports [6:31 mark]

So, what does all this mean for HID and LED grow lights? Looking closely at the video I wrote down the wavelengths of light in each ‘bin’ on the monitor, found a report about photosynthesis and color spectrum, and looked up the wavelength colors on autolumination.

Bin 1 = 300 – 420 nm = UV-A, UV-B, Violet. While mostly unnecessary, the 400 – 420 nm range is useable by plants.

Bin 2 = 449 – 480 nm = Blue. Blue is a very important color for plant growth, especially for leafy or vegetative plants.

Bin 3 = 621 – 680 nm = Orange, Orange-Red, Red. The colors in highest demand by plants, even though blue looks more important on the chart. Notice that the solid green line slopes quickly down away from UV, but has a distinct peak in red.

Bin 4 = 681 – 780 nm = Deep Red, Shortwave Near Infared. Light from 680 – 700 nm is still useful to plants.

Bin 5 = 781 – 850 nm = Longwave Near Infared. All wasted energy.

After looking at these numbers, it is clear that LED grow lights aren’t just more efficient, but more effective than HID grow lights.

Anyone with experience with any of these high quality LED grow lights please tell us about them. Even if you want to comment about how bad the old style LED panels (1/4 watt diodes) or cheap Chinese knock-offs (1w or falsely advertised 3x1w clusters of diodes) are, everyone can benefit from your input.