Top bin COB comparison
- Thread starter SupraSPL
- Start date
- Status
SupraSPL
Well-Known Member
With a COB running at 50W, 15" distance, without reflective walls in the test area, I measured a consistent 25-40% increase in intensity by adding simple painted plastic reflectors to a COB. That is primarily because it is illuminating a smaller area, the desired area. The test is easily repeatable but you are right, the gains would be much less when compared against a bare COB with the walls assisting.
I have never done that test with reflective walls in place, but it sounds like it would be worth the effort to mock a small one up around the test area. If I recall @AquariusPanta and/or @robincnn have done reflector/lens tests with and without walls.
Last edited:
littlejacob
Well-Known Member
Bonjour
At 16 or 12 inches from the canopy is a cob with a 90º reflector cover a sq/ft?
What is the best to cover only a sq/ft...with cxb 3590 36v @700mA...
Let's say a cxb3590 @1400mA alone have 1.5 foot penetration...how many more with a 90º reflector...how many more with 90º lens???
Peoples buy it to increase penetration but I never heard numbers!?!
CU
At 16 or 12 inches from the canopy is a cob with a 90º reflector cover a sq/ft?
What is the best to cover only a sq/ft...with cxb 3590 36v @700mA...
Let's say a cxb3590 @1400mA alone have 1.5 foot penetration...how many more with a 90º reflector...how many more with 90º lens???
Peoples buy it to increase penetration but I never heard numbers!?!
CU
hillbill
Well-Known Member
It seems that a naked cob would blow a lot of light out over the tops before finally being reflected somewhere from the reflective sides. Reflectors or lenses just put more of that light into a useful area for our purposes but act much different from each other in use. They both shape the 3 dimension light profile. Lenses need some distance to get their act together but then hold on, while the reflectors create an immediate wide if shallow field of intensity. Both work and somehow sound better than running a naked cob.
littlejacob
Well-Known Member
Ok I never tried with optics so I want to believe it and I know you are all...almost lol...reliable!
But what I want to know is what is the area and depth a cob with a kb 90º reflector can light?
And what kind of reflector and lens cover only a sq/ft...I know it is more a diameter but we have square shape grow space...!...Mr CREE save us make some square cobs...pleeeease!
CU
But what I want to know is what is the area and depth a cob with a kb 90º reflector can light?
And what kind of reflector and lens cover only a sq/ft...I know it is more a diameter but we have square shape grow space...!...Mr CREE save us make some square cobs...pleeeease!
CU
nogod_
Well-Known Member
Depth is relative to intensity and canopy density so impossible to say...
But a 90° reflector is easy to calculate area....
Pi (height)^2
Soooo @ a height of ~6.8" your area is 144"sq per cob
But a 90° reflector is easy to calculate area....
Pi (height)^2
Soooo @ a height of ~6.8" your area is 144"sq per cob
wietefras
Well-Known Member
Remember that Gavita PPFD matrix we were talking about a while back and then Stephenj37826 found a similar test, but with reflective walls:
and the test with no walls at all:
The fist matrix is a 3.7ftx6ft (22sqft) tent and the second one 4'x4'. So the surface area for the reflective walls is 38% bigger, yet the light density is way more than double and much more uniform. Also with a "deeper" reflector though
(IIRC it was 110 degrees for the single lamp setup vs 138 degrees for the regular reflector meant for overlapping fixtures)Of course since the HPS is 36" away from the canopy, the walls are much more important than you would see with COBs, but with COBs and reasonable wall reflection you should get a uniform distribution of light from wall to wall.
ps If taking light measurements in a tent, don't forget to close the tent when you are actually taking the measurements. Yeah yeah I know, funny you can't see the results then, but you can open a zipper up high somewhere (above the fixture) and look down. That will make a big difference already.
I also put the fixture and the meter a bit higher instead of measuring on the floor, to prevent the light falling on the bug filters covering the air inlets.
Last edited:
wietefras
Well-Known Member
Lol @nogod_
Well someone else did that on a Dutch forum. Maybe I shouldn't step into another potential mine field, but he found that mirrors actually worked best. Not just that they reflect very well (high reflectance) and also directly towards the plants (not diffuse at all), but mirrors are very easy to clean as well. They pretty much keep their reflectance for ... well a long time.
Fastslappy
Well-Known Member
hmmmm & I was about to toss 2 huge mirrors 4x 5' & bigger
note to self move to groroom
i wonder if i place on near the floor & angle it slightly to get the light back up as that changes the angle of deflection
I love reuse
REALSTYLES
Well-Known Member
Mirrors are the worst thing you can use. Why? for 1 nrrors only reflect back a portion of light visible to us. For 2 other wavelegnths are actually absorbed by it and it effects the plants. ALSO do not reflect evenly where they reflect the focal center of the light, you get hot spots reflected onto the plants that can toast them after a while. Have you even tried this theory or are you just rambling on? That's what I know about using HPS and won't even try it with my cobs due too the cobs emit mire light, but nice try proving your point.
Fastslappy
Well-Known Member
I know hot spots , got a bad burn on Strawberry cough this summer in the G/H stainless steel reflector not in use (the shop kind) that I'd left hanging on a rafter the sun hit it just right cooked sum bud bro !
realstyles ; I now remember reading that somewhere in books on mj growing I got
which is why they aren't there already in the groroom
Man the learning curve is finally starting to ease for me I start understand what you guys are talkin about
it was steep @ 1st
realstyles ; I now remember reading that somewhere in books on mj growing I got
which is why they aren't there already in the groroom
Man the learning curve is finally starting to ease for me I start understand what you guys are talkin about
it was steep @ 1st
Sativied
Well-Known Member
That's deep though.
Well if that excellent source of unbiased and trustworthy information doesn't end that discussion, NASA uses mirrors too. An appeal to authority works much better if it's actually an authority and we all know NASA doesn't want to waste anything.
They are in fact a mirroring surface and not your house mirror. What matters is its material, and the material regular mirrors are made of isn't ideal.
What do you call a community that after decades can't figure out what the best reflective material is...
@REALSTYLES:
REALSTYLES
Well-Known Member
It must suck that you can't do this
That's deep though.
Well if that excellent source of unbiased and trustworthy information doesn't end that discussion, NASA uses mirrors too. An appeal to authority works much better if it's actually an authority and we all know NASA doesn't want to waste anything.
They are in fact a mirroring surface and not your house mirror. What matters is its material, and the material regular mirrors are made of isn't ideal.
What do you call a community that after decades can't figure out what the best reflective material is...
@REALSTYLES:
That my Blue Nose named Blunt lol
littlejacob
Well-Known Member
Bonjour
Nice dog...he look cool!
Plants too...
Trimming in process...
...trainwreck hso (32 vegg and 69 bloom!) Short and efficient...find the lighter lol!
cu
Nice dog...he look cool!
Plants too...
Trimming in process...
...trainwreck hso (32 vegg and 69 bloom!) Short and efficient...find the lighter lol!cu
REALSTYLES
Well-Known Member
Nice job Jake
BuddyColas
Well-Known Member
LJ,
I have seen you post many times, but this is the first shots of your plants I have seen. Quite a harvest!
Please share the details of your COB build and grow space details.
Thanks.
dionysus4
Well-Known Member
wietefras
Well-Known Member
Lol, I knew people would go apeshit over the mirrors thing 
Mirrors use aluminium as a reflective material and that's exactly the same as used in most HPS reflectors. Silver would be better of course, difficult to find mirrors with that though and the difference is marginal (apart from the price difference which is huge).
So you are grossly exaggerating the influence on the spectral distribution by mirrors.
Of course there are reflective foils that reflect even better than mirrors, but they are less easy to clean and cost a whole heap more.
What's most important though, get direct reflections and not diffuse. Especially COBs emit diffuse light already.
Yeah people keep saying that, but several people put mirrors in their grow room and with those they get the highest light density. Perfect wall to wall light distribution as well. It's like having a light on the other side of the mirror. Just the way it should be. I don't use mirrors myself, but I did test the reflection and in fact they do reflect better than the walls of my grow tent. Just put a mirror next to your wall and see what it does to the light intensity on your light meter.
Mirrors use aluminium as a reflective material and that's exactly the same as used in most HPS reflectors. Silver would be better of course, difficult to find mirrors with that though and the difference is marginal (apart from the price difference which is huge).
So you are grossly exaggerating the influence on the spectral distribution by mirrors.
That's just plain nonsense. Who's rambling now? Mirrors are perfectly flat. How could they create a hotspot. You must be confused about poorly fixed mylar or something.
Of course there are reflective foils that reflect even better than mirrors, but they are less easy to clean and cost a whole heap more.
What's most important though, get direct reflections and not diffuse. Especially COBs emit diffuse light already.
- Status