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Don’t waste a Watt – Which Reflector Do You Need?

Don’t waste a Watt – Which Reflector Do You Need?

Alex Grady

Around 50% of the light emitted by your bulb is beamed down by your reflector. It's key that you get the right one. Here's how to pick.

Types of Reflector

There are three main types of reflector.

Open ended


These are the most popular type.

Open ended reflectors let lots of heat produced by your lamp escape.

This generally means that they can be placed closer to plants than closed-end reflectors. If headroom's an issue in your tent, they're great.

You can, however, generally get a more precise footprint with a closed-end reflector.



Closed-end reflectors (like the Northstar) often have a more precise and uniform spread of light.

However, you normally need position them higher up than open-ended reflectors to avoid heat problems. Some growers use a light rail with them during summer to get around this.

The Silver Parabolic reflector is slightly different. It has a vertical lamp and air vents, which allows a lot of heat to escape. Reflectors like this are very pupular in the US!

Air-cooled Drakstar refector


These reflectors are the best ones at removing heat.

Reflectors completely surround your bulb, creating an air-tight tunnel. Air is blown through this tunnel, over the bulb to remove heat. It's great in summer!

To make sure light can reach plants, the reflector bottom is glass. Keep it clean the glass panel to minimise the amount of light lost through it.

You will need to use an extractor fan ducting and fasteners with this light. To make life easy, you can buy everything together in air cooled light extraction kit. Both 5" kits & 6" kits are available.


Don't suck through the reflector - always blow to prolong fan life.


We've sampled many types of this reflector, but have yet to find one that works. With this type of reflector, you get 2 main issues:

1. Too much light is lost through the water

2. Water and electricity do not mix well - it's a safety issue, folks. One mistake during assembly and you've had it.


There are lots of reflective materials on the market - normally, you get what you pay for.

You may save a few quid by buying a cheap reflector, but remember every 1% of reflectivity costs you up to 0.5% of your yield.

Getting a good reflector (and replacing them often) is easily one of the easiest and cheapest ways of improving your yield.

The three main materials are:

  • Stucco
  • Hammertone (hammered aluminium)
  • Vega/MIRO
Stucco & Hammertone - 80 - 85% Reflective

Stucco & Hammertone - 80 - 85% Reflective

These reflectors are good but no cigar. What you really want is Vega/MIRO aluminium.

Vega/MIRO aluminium - 96% - 98% Reflective

Vega/MIRO aluminium - 96% - 98% Reflective

This is the best material to use. Reflectors made from this material aren't that much more expensive than cheaper ones - maybe £20 - £30 extra or so, depending on which ones you compare. For that, plants get so much more light!


The shape of your reflector needs to match the shape of your area. Otherwise, you can end up losing light to walls, or get areas in your tent that aren't covered by your reflector.


in a square, XL Tent, the Northstar reflector is ideal.

If you've got multiple light, you'll need to split your growing area into sections. Your reflectors shape should match the shape of each section.

Northstar reflector


If you want to really nerd out when picking your reflector, think about the way light works.

Light, like all wave energy travelling through any atmosphere, gas, or liquid, it's subject to four main physical effects:

1. Attentuation (loss of intensity)

a) In air, the loss of light over a distance is quite high.

Light in your grow room is subject to the Inverse Square Law - where light spreads out to cover a bigger area as it gets farther away from your lamps.

So if you double the distance between the light and plants, you'd need four times as much light to get the same intensity, because it has spread out.

b) As light passes over surfaces (like reflectors) some light is absorbed and scattered (or attenuated).

So it's your reflector's job to minimizing attenuation of light, using the right materials.

2. Refraction (light beams change directon)

Refraction happens when light energy is bent from its straight line path through the air. This is caused by changes in humidity and temperature in the air. This doesn’t affect us too much when growing indoors.

3. Diffraction (light beams spread out)

Light energy (like all kinds of wave energy) is able to bend around objects in it’s path.

This is purely dependent on the wavelength and frequency of the light. As wavelength increases (frequency decreased), diffraction increases and the scattering effect is also reduced.

4. Reflection (light is thrown back instead of being absorbed)

With your grow lights,the amount of the light reflected (and attenuated) depends on your reflector's surface size, material and distance from your bulb. The angle at which the light hits the surface is also key.

Light needs to be reflected down with as little loss (attenuation) as possible, and reflected in a way that gives a good, uniform spread.

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