Conducted tests for best reflective surface for your lights/hoods

[Perfect Sun LED]

To get a 24.2% increase, use white paint on under your hood.

You want your hoods to reflect the most light, giving your canopy the most lux. Here are the results of my tests.

What are the best reflective surfaces? Some of the results of my experiment might surprise you. I used a 23w CFL bulb for the test. I also did a few tests with a 64w cfl. Remember 23w call is equal to 100w incandescent, and 64w=300w.

You can watch the video if you want to see me doing the experiment.

Sun

on a bright day, hottest 1-3 is 100,000 lux. On a cloudy day, but bright, not dark 3,000-10,000 lux.
The following materials were only used as a backdrop part of the hood, not the side panels, which also increase lux more. So use side panels.

Human Skin

Before I used my hand as the back hood, LUX 10,260. After hand as a reflector, with hand touching the bulb because you get higher LUX output if the reflector touches the cfl bulb, 11,010. That is about 750 more lux, which is a lot considering the low lux of this bulb.

Sheet Metal

The results amazed me. Skin is better.
10,260 before 10,730 after. 470 lux increase.

Now 470 doesn’t seem like much, but when used on a 64w (300w equal) it jumped from 16,300 to 19,300. That is with just back piece, no side panels. So about 3,000 more lux. The more powerful the bulb, the more lux you get from it with a good hood.

NOTE: To get the most out of CFLs, build a good hood with white material on the inside. Be sure it has the back, side panels, and front and back panels. All panels should be at about a 45 degree angle. If you can, make the cfl touch the back of the hood, or get as close as possible.

Flat white paint on sheet metal
Before 10,260—after 12,600. 2,340 lux increase.

That is huge for this small bulb. That is with only a back, no panels. With panels, the lux increases even more. That is from one standard 23w cfl at 2 inches away from censor, about where you want to be with such a bulb. Put 4 of these together under the same hood, and you get a huge increase in lux, than if they were not in a white hood.

White beats everything I tested. Here are more materials tested.

Mylar, like inside a grow tent
Before 10,170—after 11,030, 860 lux increase. That's only an 8.4% increase. BOOO! Mylar sucks.

About as effect as human skin. Not impressed. The white plastic is just as easy to clean, so why not make tent with that?

Semi Glossy White kitchen wall, so bumpy texture

Before 10,500--after 12,970, Lux increase 2,400.

This outperformed the painted sheet metal, which is surprising to me because the wall is bumpy. I would have thought also that semi gloss would be less effective. The difference isn’t much and could be that whole plus minus thing for tests. It seems anything white works equally well, even white plastic, which I tested, but not in this video.

Aluminum hood. Standard material in most hoods. That lump stuff.

Before 10,500—after 12,170, Lux increase 1,670.

Not bad. White would be better, so I am going to paint mine. I will then test the lux difference at a foot away and see if it helps.

Mirror

Before 10,400—after 11,280, lux increase 880.

About as effective as mylar and human skin. Not so good.

Brown Towel
Before 10,400—after 11,460, lux increase 1,060.

That blew my mind. A rough, brown towel out preforms, mylar, mirror, sheet metal, and human skin. Amazing. WTF?

Darker, pink-maroon wall.

Before 10,400—after 10,900, lux increase 500. Boo.

White, bathroom door, semi-gloss paint, flat surface

Before 10,300—after 12,800, lux increase 2,500. That is a 24.2% increase. Amazing.

Grey-blue wall. Sort of a light color.
Before 10,400—after 11,780, lux increase 1,380. Not bad.

[/SIZE]CFL test 64w 300w equal. This is a huge bulb. At 4 inches away.

Sheet Metal
Before 16,300—after 19,300, lux increase 3,000.

Flat white paint on sheet metal
Before 16,300—after 22,100, lux increase 5,800. That is a 35% increase!!! So, yes, more cfls or a larger cfl produces even more like under a white hood than less cfls or a smaller cfl. We went from 24% increase with the 23w cfl to 35% increase with the 64w cfl. 11% increase.

As you can see white rocks. That is just with a back reflector. Put on side panels, and bam. At 4-6 inches away with my cfl hood, bulbs sideways inside it, bulbs not touching the back reflector like they should, with side panels, all white inside, I get 30,000 lux. That is pretty awesome. When I mention the bulbs inside, I will mention their equal to incandescent bulbs.

1x 300w, 2x 150, 1x 100, plus a small 60w red bulb.

I will post the video of me doing the test once it is finished processing.

 

[oldman60]

I wonder why your results are different than virtually every other comparison I've read?

 

[Perfect Sun LED]

Not sure because I haven't read them, but maybe they are trying to push a product or something. Or maybe they didn't do the tests. Not sure. I'm uploading the video of me doing the test right now onto Youtube. I will post the link once it is finished.

 

[Perfect Sun LED]

But in this grow bible I read, it said that flat white was like 98 or 99 percent reflective. It makes sense because white reflects all colors, black absorbs. Metal is sort of like a mirror. In fact, a mirror is silver with glass in front of it.

 

[Perfect Sun LED]

Get 35% more lux/lumens/brightness from your CFL or any bulb - YouTube

The link to the tests.

 

[H-factor]

Now I need to paint my little grow box flat white

 

[Perfect Sun LED]

Personally, I would go with semi gloss white that way it is easy to clean without removing paint.

Also, semi gloss is easier to find heat resistent paint. And I got a slightly higher preformance with the semi glossy on the bathroom door.

 

[Fuzzy Duck]

I like the part in the youtude vid where you tested the 300w giant cfl for lux at 2" & 4" that was a prime example of the Inverse square law of light effect

Which CFLs suffer greatly with hence we always hang em 1" above the plant to get best use of aviable light.


As bulbs light source degrades over time (mainly the first few months of use) e.g diminshing qualitie of light you should be able to measure that effect with the lux meter.

From what i recall...

HPS/MH may degrade by 30%

CFL may degrade by 15% to 20%

T5 may degrade by 10% to 15%

This may varie with no name brands & brand name bulbs tho... could be an interesting project.

 

[Perfect Sun LED]

yeah. I'm keeping up with my bulbs to see how much they diminish over time.

 

[Fuzzy Duck]

yeah. I'm keeping up with my bulbs to see how much they diminish over time.

I look fowards to the results

Little graph of some bulbs degrading over time

 

[Perfect Sun LED]

I am about to do some test with a lux meter and green plastic over the meter to see if it filters the green out, making it read more like a PAR meter. Cyan might work best. I have been searching for photo filters that block all green, but let blues and reds through.

 

[Perfect Sun LED]

I just figured something out. The distance the light is away from the censor affects the increase in lux. I used the same 23w cfl bulb, but this time I put it about an inch away, which gives 19,500 lux. When I place the flat white behind it, it increased by 6,000, instead of 2,340. So with a proper little white hood with side panels, you could turn a 23w (100w equal) into more than a 25,000 lux bulb, if you keep it an inch away from the bud, which is totally possible with this bulb. It shouldn't bleach the leaves. Put two of these under a small white hood and you could probably get a decent bud from each hood. That is, place each hood an inch away from a top.

The reason for this. About half of the light from the bulb faces away from the plant, and thus flys away and is not absorbed. The other half is facing the plant, and so hits the plant. However, if you place a white plate behind the cfl, it reflects the light that would otherwise fly away in the room, away from the plant. Now, that light has to travel the distance it takes to get from that side of the bulb, to the reflector, if the reflector is not touching the bulb, and back to the plant. This is why the lux drops quickly the further the reflector is away from the bulb because the light must travel that much farther. The light from the back of the bulb also must travel the distant of the length of the cfl itself, so the light produced by the back of the bulb is like a whole inch further away from the light coming from the front of the bulb. This is why you don't see a double in lux by using a hood.

So keep your reflector as close to your cfl as possible, if not touching it.

Interesting Green reflector PAR?

So, I had this idea. First measure the increase of lux from an inch away using flat white. I got 6,000 increase. You get less increase the further the bulb is from the censor. Anyway, white reflects all colors the bulb puts out. I thought, well, if I use a green reflector, it will absorb all the colors but green. It reflects green, which is why the object looks green.

Green reflector = 3,500 increase, so a little over half of what white reflected. Green would be the worst color to use as your reflector because plants don't really use green. It's why they are green. They reflect that color.

This should show that CFLs produce a lot of green. I tested blue, yellow, and red.

Red = 1400 increase. (Might be worth using a red hood when in flower because you are reflecting only the red spectrum of the back side of the bulb onto the plant, thus giving it a big red increase, which is good for flowering. If you use white, you also increase the back half's yellow, blue, etc. Something to experiment with. Use a blue hood for flowering?

Blue = 900 increase. This tells me that CFLs don't produce much blue.

Yellow = 2,000 increase.

Keep in mind, there are a few more colors that CFL's might produce a bit of. Also the color green is actually yellow and blue, but not sure if this matters when reflecting light. On top of that, there are different greens. The green I used might not cover all the green nm spectrum. I want to try a similar experiment with using a filter that filters out all the green nm range, 510-590 or something.

 

[Perfect Sun LED]

I wonder if I use a filter that filters 510-590, if it would turn a lux meter into a par meter. After all, a par meter measures the light available for photosythesis. If you filter out all the green light, then you are left with what plants can use, but perhaps I should also filter out the yellow. Not sure if par meters measure yellow.

 

[Perfect Sun LED]

I conducted another experiment with interesting results.

I place the censor so the back side faced the light, thus resulting in no reading at all. No lux was measured for no light hit the censor. Then I placed a reflector in front of the censor, this way the light would bounce off the reflector and that would be the only light the censor picked up, the reflected light.

A red reflector will reflect red light, green will reflect green, etc, so this will give a good indication of how much percent of the light is red, green, blue, etc. I kept the censor an inch away from the reflector, but each light was a different amount of distance from the reflector to give high readings. cfls were about 3 inches from the reflector. LED about 8 inches. Hps about 16 inches.

First I tested the 23w cfl, 2700k.

White 3,500
Green 1,160
Red 1,190
Blue 840
Cyan 820
Yellow 2,730

As you can see, warm cfls produce more green and red than blue, and a lot of yellow.

CFL 500k 23w

White 3,000
Green 1,200
Red 1,200
Blue 840
Cyan 2,000

Ad blue and red together, and it is 68% of the value of white. This clearly doesn't show the PAR of the bulb, but it should give some indication of the color output?

I forgot to test yellow, but I am sure it would be high. So the 5000k cfl produces just about as much red and green, but more cyan. Same amount of blue. I find this interesting. Seems 5000k might be a good bulb for veg and bloom.

HPS

White 40,000
Green 10,000
Red 14,000
Blue 9,000
Cyan 8,000
Yellow 22,000 55% when yellow is compared to white

Add blue and red, and it is 57% of white.

The numbers are what I would expect, higher reds than blues. The green is weird. I couldn't get it to change.

LED

White 30,000
Green 7,500 (about the same as hps, percent wise)
Red 15,000 (higher percent than hps. Hps has 35% when red is compared to white, and led has 50%.)
Blue 12,000 (Higher % than hps.)
Cyan 10,000
Yellow 17,000 56% when yellow is compared to white

Add blue and red and it is 90% of white.

So although this doesn't show a par rating per say, it does show what lights should have a better par rating. LED wins hands down. CFL is even better than HPS, but HPS puts out enough lux to make up for it. Also, check this thread out about how green is actually very effective for photosynthesis do to green being able to penetrate into the leaf more and get causes chemical reactions inside the leaf.

Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong Whit

 

[cgkone]

what kind of LED did you use?

 

[Perfect Sun LED]

i bought it from
ledgrowlightmanufacturer on ebay

they havent named their leds but they do show what parts they use.

 

[resohrpq]

Great thread. Keep posting results.