JoseHempSeed

I've been trying to get a better understanding of the relative merits of various lighting techniques.

After reading the discussion groups, and a few books on lighting and cultivation, I became even more confused - while there is plenty of advice, much of it is contradictory and does not make much sense.

However, one fact is clear - the lighting intensity is critical to the garden's health.

So, having a pretty strong technical background, I did a lot of research, and then measured the output of several types of commonly used garden lamps. For me, a chart or graph is much easier to grasp than a series of numbers. Since I needed some perspective on the different lamps, and after learning so much from reading and corresponding in this group, I thought I'd share the fruits of the research. Sorry if this is redundant or has already been done... So here's what I came up with. I hope someone finds this useful.

Some notes on reading the chart:

1) The bottom scale is in Exposure Value. This is a very common photographer's measurement, so if you have access to a light meter (or higher-end camera), you can easily measure your own garden light and see where it fits onto the chart.

2) A change of ONE EV means DOUBLE or HALVING the light. For example, going from an EV of 14 to 15 is doubling the amount of light. Likewise, you can see that a 400W MH @ 12" is roughly 1/4 (1/2 x 1/2) the brightness of the noonday sun.

3) All the measurements were taken along the centerline of the reflectors - the brightest part. The light decreases rapidly as you move radially away from the centerline.

3) I couldn't come up with anything more powerful than the 400W/430W HID lamps. Maybe someone would be interested in loaning me a kW HID for a few weeks? ;-)

4) I used the same reflectors for like lamp families. So the plot is normalized to these; it's a very good comparison. Photo attached.

5) All the lamps are past their 'initial output' stage. They are closer to mid-life; they should represent the 'mean lumen' output.

6) The chart considers only light brightness, or intensity. It does not account for the spectrum of the light. That's another subject, as there's already plenty written on that.

Grow On!