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!

JoseHempSeed

the chart

Attached Thumbnails

 

JoseHempSeed

the reflectors

Attached Thumbnails

 

Corrosive

Great post José,

Thankyou

JORDANSDAD

great job on the stats there sir, people will refer to this often. nice plants in the pic!! latr, J D.

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Childish

thx

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greenmachine

thanx Josè, and like I once said, you don't sound junior. Hey CHILDISH, he just might take your place one day,
Just kidding, there's a lot more to know about MJ growing , but ***T, he/she surprises me all the time.
You say that my light sounds a bit small but were can it be placed on that chart you posted, just to simplify.

JoseHempSeed

hey guys, thanks for the positive comments on the post, i'm glad you find it interesting, and hopefully even useful.

hey greenmachine, i tried desperately to come up with a 250w mh, but couldn't. i know it's a very popular lamp, so i'm still looking...

anyway, the 250w mh has about 59% the mean lumen output when compared to the 400w mh. so that should put it at about 1.9k lumen/ft. sq. @ 12", right about where the 25W compact fl. is on the chart. (but don't forget the 25w cf is measured at 2" - the mh is much brighter than that since it's measured at 12" - meaning a bigger garden).

you can probably squeeze a few lumen more, since the 250 mh's are available in the base up variety - using the round sombrero type reflectors - which i suspect are slightly more effecient than the half-cylindrical type i used for the measurements.

Grow On!

wahit

Great post dewd !
It helped me a lot

Thanks !!

Xzoomd

great reference!


maybe others with meters can add to your chart. like the 250s 150s and 1 Ks. $.02

zoomy