All lights were warmed up for 30 min before measurements. The 42 watt CFL bulb is longer than the reflector on the lamp so an aluminum foil extension was made to extend the reflector 3" beyond the end of the bulb. Measurements were made both with and without the reflector extension.

One 42 w CFL bulb in a lamp style reflector. Measurements taken at the center of the cone of reflected light:

Distance from nearest point of bulb surface without extension:

0" (touching bulb) 8000 fc
3" 2300 fc
6" 850 fc
12" 280 fc
24" 108

Light level w/3" reflector extension:

0" n/a
3" 3850 fc
6" 1700 fc
12" 450 fc
24" 120 fc

Light from a point source with no reflector drops off as the square of the distance from the source. In other words, if you move twice as far from the source, the light drops 2 squared or 4 times.

The whole point of a reflector is to concentrate the light in a direction and thus reduce the loss with distance. You can see from the two CFL measurements above that allowing the lamp to extend beyond the reflector significantly reduces the light in the reflected direction. (it allows light from the extended bulb to go off in a wider angle). If you used no reflector, the results would be dismal.

As stated, this was with the 42watt CFL, not the big guns you purchased but the same variables would apply, just in higher numbers. The numbers were also taken on a six mo. old bulb, not a brand new bulb. I know regular fluoro tubes decline rapidly once they are turned on. I don't know the fc drop off in a CFL but would assume they decline too.

For reflectors, I would try FarmTek or a hydroponics store. Mail order hydro stores would probably be cheaper than a local walk in store but you might get a better idea of what to look for if you could see it locally. Who knows, the local store might be in a giving mood since it is the holiday season.

Reflectors would make a great b'day present :>)

Brooke

The book I studied from before setting up my basement lights suggested (for HIDs), that you could use a lower wattage, (say 400 instead of 600 or 1000) and place them near enough together so the area of light coverage overlapped.

That creates a third area of high light *between* the two lights. In that way two or three 400W placed correctly create a much bigger high light area than a larger-watt bulb (and cooler as well, so you can place the plants nearer)

I set up my Wonderlites the same way, to create a high light area between pairs of them.

Hope that's clear. Don't know a better way to say it.

Brooke

I think I remember reading on one site that they are positioned so that the light from the individual LEDs overlap one another. They didn't state that the reason was to increase the intensity, but with those low power consumption and low heat generating things, why not stack them tight if it increases the intensity.

Bob

Brooke

Brooke

No commercially produced 40w bulb exists with an 8000 lumen rating, neither home or industrial usage.
CFL's twice the size are approximately 7000 initial lumens.
Commercially produced 40w cfl's are in the 3000- 3600 lumen range regardless of K rating.

At a distance of one inch from the bulb 2347 footcandles is being delivered to the plant.
[NIST Certified meter]

*Note: Lumens = Footcandles at 0 distance.
Degredation at a fraction of an inch is significant.

A 40w bulb is a 40w bulb, spiraled or straight.

We thought it a benefit to new orchid growers to ammend the above measurements.
CV
Drs Charles and Vanessa Varzsegy MD, Phd

A footcandle is a light intensity measurement and a lumen is a light flux measurement - light per unit time.

Agreed a 40 watt bulb whether curly or straight, takes the same amount of energy to produce light. The CFL light is concentrated in a much smaller area whereas the straight tube produces the light over a longer area, but less intensity over the entire length.

Who is Drs. Charles and Vanessa Varzsegy MD, PhD and is their degree in light measurement? A light meter works great for me.

Brooke

Brooke - your measurements with and without the reflector definitely show the importance of reflectors - someone on another forum showed the same thing with T5s actually - it makes a huge difference! Just for the record, I have *heard* that aluminum foil is bad material for making reflectors, as no matter how smooth you get it, it still scatters the light undesirably. Apparently, plain white is the best reflective material - it would be interesting to try the measurements with either 3" tin foil extenders, or 3"white paper extenders.

Lacontessa - I was also a bit confused about the lumen-foot candle thing...hard conversion to do but I found: http://www.lightingdesignlab.com/articles/metrics_quantity/metric_quantity.htm
(very good diagram!).

From what I've read, essentially foot candles/lux is a measurement of the amount of light that falls on a certain area (aka intensity) whereas lumens is simply the quantity of light flying out of a source. 1000 lumens spread over 10 feet = 100 foot candles. 1000 lumens spread over 1 foot = 1000 foot candles. 1000 lumens spread over 0.1 foot (which is roughly what you get right up at the bulb) = 10,000 foot candles.

If the lumen rating on bulbs describes essentially the amount of light flying out of the bulb, then it I'm not sure you're correct in saying that lumens = foot candles at 0 feet....theoretically, by the definition of foot candles as light landing over an area, as your area approaches 0 (which will happen as you move closer and closer to your point source) your foot candles can approach infinity as the amount of light your outputting is concentrated over a smaller and smaller area.

Btw - is this actually clara from before with the big bertha?? why the name change?!?

I believe (if understand what I read correctly). Someone please correct me if I'm wrong.

Now say 3000 lumens is the total light output of the bulb. The problem here is that this is total light output in all directions, so not all 3000 lumens will travel to your lightmeter/plant. If we were able to direct the entire output of the bulb to 1ft by 1ft (that is 1 foot away from the bulb) section of plants those plants would be receiving 3000fcs. Unfortunately light escapes and we're not that good a controlling it (and you probably want to cover more than a 1x1 section of plants. So I am going to verify for you Brooke's measurements at 12" with a reflector.

Assumptions:
Bulb lumen output (from package) = 3600 lumens
Bulb's + reflectors footprint at 12" away = approx. circle of radius 1.5 feet = PI*(1.5*1.5) = 7 sq ft
All light output from bulb is directed at footprint, lumens emitted away from the surface are bounced back towards it by the reflector.

Calculation:
footcandles = lumens / area covered by light
= 3600 lumens / 7 sq ft
= 514 footcandles

Of course, no lighting system is this perfect, so a good chunk of the light is lost, to me the 450 fc measurement seems completely logical.

Thanks, Brooke!

Sc

Also, about T5's. I love the look of T5's-- just so sleek and bright-- that I plan to install some in my light room this fall. One of the light movers died, and I'm not going to replace it. The T5's would cover some of the now-unlighted area. More easily raised and lowered on a pulley, too. The HID's require real muscle to raise or lower.

I'm thinking about them for my west window, too, for the same reasons.

So I would really appreciate you sharing all the information you collect about your T5's once installed. From your own measurements and whatever you read as well.

Who is Drs. Charles and Vanessa Varzsegy MD, PhD and is their degree in light measurement? :-)