Hello Professor Lee,
I want to buy my first HID grow light, and there are a ton of choices at my local head shop. I know that I want to buy a HPS light, but I don’t know what kind of fixture I should get. I don’t want to spend a lot of time having an in depth conversation with a sales person. I can afford a 400 watt lamp and will be growing in an area about a square yard in size. Any advice would be great!
Sneaking into a grow shop wearing a trench coat and dark glasses is a rite of passage many growers have had to make. I certainly remember when I had to do it. Buying my first light was a lot like having sex for the first time. Awkward, I did some basic pointing and grunting, paid a little cash, and it was over really fast. A 400 watt lamp will work quite well in the small space you plan to use as long as you compensate for the heat generated by the lamp. An aggressive ventilation/circulation system will do the trick.
With smaller cone style vertical fixtures the bulbs orientation directs very little of its initial light towards the plants. Instead the light is directed outward and then reflected off the cone towards the plants. I find this method inefficient, but superior to a naked bulb.
The larger wide cone vertical fixtures can have diameters of three or four feet. They cast light out over a wide area. This is great for combining several lamps over a large garden. Especially when a grower wants to combine different spectrums like those emitted by MH and HPS lamps. These fixtures wouldn’t work well with your setup.
With a small space and a single light source, like the HPS you plan to get, I strongly suggest a horizontal fixture. It’s more efficient than vertical models because more of the light bulbs surface area is exposed to the plants. This means that more of the bulbs initial light will be directed toward the plants. In my opinion this is the most productive fixture for your needs.