BuddyColas
Well-Known Member
OK, I'm in...link please.
Top bin COB comparison
- Thread starter SupraSPL
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Stephenj37826
Well-Known Member
Look up diy tech talk thread in this section
wietefras
Well-Known Member
Did you use reflective walls? Cause the tests I have seen, a COB was tested in open space to measure a tight grid of intensities under the COB, add a reflector/lens and measure the grid again. Obviously the intensities will be higher with the reflector/lens mounted
A whole room full of these things with reflective walls will have an "average PPFD" = ("PPF produced by the lights" - "losses" ) / "surface area".
So the only way to increase average light intensity over a fixed space is by increasing PPF or reducing the losses. Adding reflectors/lenses only increases losses unless you have big wall reflection losses. In which case fixing the reflective walls would seem a more efficient option to me. Only the light that hits the wall then hits a reflector (the wall) and not the light coming from COBs in the middle that otherwise never would have hit the wall.
The way I see it, reflectors/lenses are only a must if you insist on not mounting properly reflective material on your walls or if you want greater height between the lights and the plants.
BTW diamond foil is not a good reflector for COBs. They give a very diffuse reflection which can send your light to the ceiling. Get something flat and shiny on the walls for direct reflections. The light is already diffuse enough from the COBs.
I also doubt those semi-translucent white plastic reflectors reflect light better than a shiny metallic material on a wall. In general matt white materials are good for diffuse reflections and seeing how they light up they are obviously absorbing quite a lot of light too. Reflectors would be bad for uniformity of the light distribution too. The foto's I've seen the footprint was way too sharply edged.
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Stephenj37826
Well-Known Member
I'd like to see just the reflector adapter used. Also the beam angle is 115° but there is light spillage all the way to 165° +. Correcting those would be beneficial. Also if you are running isles it's a waste for sure to be lighting isles and this can somewhat avoided by reflectors/lenses at least at the isles. If letting the light reflect off the walls was best then all the hid reflector manufacturers have it wrong. I'll take my 5%-10% loss and keep most of the light off the walls as much as I can. To each his own though
wietefras
Well-Known Member
Indeed it's basically matter of replacing wall losses by reflector losses. So if you don't have reflective walls (or no walls at all) then reflector losses will be less than wall losses. When you do have nicely (direct!) reflective walls, the wall losses will be less than the reflector losses.
Even with reflectors you are still going to lose light when your walls don't reflect well enough though. So in the end I'd say reflective walls will be the most efficient option. Seeing how you need them anyway and walls only lose light on the fraction of light actually hitting the wall, instead of taking 5 to 10% from every COB.
Apart from the reflection losses, clear COBs give you much more uniform light distribution and more diffuse light and therefore better penetration of the canopy as well.
Also you would need to keep the reflectors clean and replace them every year. Probably even more often. If Gavita says their miro silver reflector lasts a year, then you can bet those cheap plastic things don't last that long.
HID is a completely different story since they need a reflector to get the light down. Those reflectors do tend to have very wide beam angles though. The standard Gavita 1000W pro reflector has a 138 degree beam angle for instance, so they most definitely need to overlap with neighboring fixtures or highly reflective walls.
Even with reflectors you are still going to lose light when your walls don't reflect well enough though. So in the end I'd say reflective walls will be the most efficient option. Seeing how you need them anyway and walls only lose light on the fraction of light actually hitting the wall, instead of taking 5 to 10% from every COB.
Apart from the reflection losses, clear COBs give you much more uniform light distribution and more diffuse light and therefore better penetration of the canopy as well.
Also you would need to keep the reflectors clean and replace them every year. Probably even more often. If Gavita says their miro silver reflector lasts a year, then you can bet those cheap plastic things don't last that long.
HID is a completely different story since they need a reflector to get the light down. Those reflectors do tend to have very wide beam angles though. The standard Gavita 1000W pro reflector has a 138 degree beam angle for instance, so they most definitely need to overlap with neighboring fixtures or highly reflective walls.
hillbill
Well-Known Member
The light bouncing off the led reflector has traveled a very short path before being redirected where as those photons have lost a lot of punch at the wall. Having used lens and reflectors as well as no enhancements, I really am liking lenses best, just as I did and do like 5w LEDs with lenses.
I'm also curious as to if anyone has noted and documented any color shift with lenses on cobs.
I'm also curious as to if anyone has noted and documented any color shift with lenses on cobs.
in "air" transmittance is NOT 100%
cdgmoney250
Well-Known Member
Specifically for testing I did not use reflective walls. Once spacing was achieved (one COB every ft2), I measured at distance with reflectors and without. The difference in output was close to 30% greater w/reflectors but sadly I didn't record any of this testing. Just the finished product.
Adding reflective walls once a certain ppf is achieved, will only increase the amount of light in the given area you want it. My grow room is fitted with "diamond foil" insulation for reflectivity.
You seem to have contradicted yourself in the same post.
How would reflector losses be higher if the intensity measured with reflectors is greater than without, over a given area?
Are you familiar with the inverse square law?
Have you actually tested your different "theories"?
I have.
And my test results pretty much contradict most everything that you have said in your post."
Reflectors bad for uniformity???
wietefras
Well-Known Member
I'm not contradicting myself. I'm not sure where you want to go with the inverse square law, because it doesn't actually apply in this case. Your test results contradict nothing from what I have said either.You seem to have contradicted yourself in the same post.
Are you familiar with the inverse square law?
And my test results pretty much contradict most everything that you have said in your post.
Reflectors bad for uniformity???
Maybe an example will help you understand. You hang the COB in a dark room with no reflecting walls and measure the light intensities over a square foot at 12" under the light. You see an average PPFD of 255umol/s/m2 and a maximum PPFD of 415umol/s/m2 right under the COB. Then you add the reflector and measure again. Now you get an average of 329umol/s/m2 over that square foot and a maximum PPFD of 620.
So what happened? Did the reflector increase the light output from the COB by 50% (based on max readings) or by 30% (based on average)? Of course it didn't. The reflector simply forced the light into a smaller area and since you are only measuring a small fraction of the entire footprint, the COB with the reflector will put more light in that small area and less outside. The reflector does absorb light though. So the intensities in that small square are much higher yet obviously the reflector will have cost you some of the light emitted from the COB. See how that works? Higher intensities in a smaller area yet less light in total.
Inverse square law applies to non directional light being sent out without being confined by reflective walls. Like in open space (or a dark room with black walls and a measuring square under the light). It basically expands like a sphere with an ever growing surface which grows quadratic with distance. When you have reflective walls (or reflectors on the COBs) you force the light back and it doesn't follow the inverse square law anymore because it can't expand like a sphere anymore. The only thing losing you light in a grow room is things like walls, reflectors and floors. Oh and the transmittance of air of course ...
Obviously even with reflective walls you will still see that you are left with less light as distance between fixture and canopy increases. In grow rooms (with reflective walls) this is more a linear decrease though. It depends mostly on the surface area of the wall being lit up and that doubles with doubling the distance.
If you had 100% reflective walls the light would keep going pretty much forever until it hit the floor or the plants and you could hang your light as high as you want. Like with glass fiber cables. That's when transmittance actually comes into play.
Reflectors don't create light. They bundle the available light tighter and in doing so actually lose some light. Walls also intended to keep the light inside the grow area and these also cost light. So really all you are doing with reflectors is trading off wall losses vs reflector losses. This can work out or not depending on your setup. Diamond foil is actually a bad choice for reflective material for COB lighting as is having no reflective walls at all (which is far far worse obviously). So indeed those would be situations where COB reflectors will help reduce the losses some.
Reflectors are bad for uniformity. They produce sharply bound circles of light while the unencumbered COB shines a much more evenly spread light.
REALSTYLES
Well-Known Member
I'm gonna have to disagree with you on the shiny metal reflector. SupraSPL did a test and the flat white did better
cdgmoney250
Well-Known Member
@wietefras
Wow, never mind.
Wow, never mind.
no I just corrected your factually incorrect statement.
no matter what you do reflection on walls will not reflect as much light as a good reflector on the cob itself. walls get dirty and dusty as opposed to a well designed sealed reflector. To match a good reflector you will need 90 plus reflection on the walls.
I'd much rather clean the protective glass over a lens, than scrub walls.
You keep hounding on walls walls walls NOBODY denies that having good reflection walls is a plus to the overall growing environment. I use them all the time. BUT its not a substitute for a well designed light that manages to keep most of its light onto the plant canopy without excessive spread .
wietefras
Well-Known Member
@REALSTYLES, On another forum I have seen tests and the shiny surfaces metallic beat the flat white ones by quite a margin. They got around 20% more light over the entire grow area by switching from white plastic or flat white paint to shiny alternatives. Especially plastics that let some light through performed really poorly.
@cdgmoney250, It's ok if you don't understand it right away, but feel free to ask for more clarification where needed.
@PurpleBuzz, You didn't correct anything. You added an irrelevant statement. Transmittance doesn't reduce "photon punch" either.
The thing with walls is that you have much less light hitting them than would hit the reflectors. I don't believe that a semi-translucent flat white plastic reflector is going to reflect better than a reflective foil, but even if it did, the walls would still have much less light on them than you get on the reflectors that are mounted on all COBs by quite a margin.
I'd love to see you clean a COB reflector. Reflectors do get dirty. After a few grows you will need to clean them. I agree a lens would be easier to clean.
@cdgmoney250, It's ok if you don't understand it right away, but feel free to ask for more clarification where needed.
@PurpleBuzz, You didn't correct anything. You added an irrelevant statement. Transmittance doesn't reduce "photon punch" either.
The thing with walls is that you have much less light hitting them than would hit the reflectors. I don't believe that a semi-translucent flat white plastic reflector is going to reflect better than a reflective foil, but even if it did, the walls would still have much less light on them than you get on the reflectors that are mounted on all COBs by quite a margin.
I'd love to see you clean a COB reflector. Reflectors do get dirty. After a few grows you will need to clean them. I agree a lens would be easier to clean.
littlejacob
Well-Known Member
Bonjour
Do you heard about the new secret Jardin orca tent?
We talk about reflective walls but is mylar the best at this game? Or is it Orca tent? (369€...390$ the 4x4...not cheap...but if it is really that effective!!!)
CU
Do you heard about the new secret Jardin orca tent?
We talk about reflective walls but is mylar the best at this game? Or is it Orca tent? (369€...390$ the 4x4...not cheap...but if it is really that effective!!!)
CU
REALSTYLES
Well-Known Member
You need to shut up. You are just guessing. Have you done any test or you just running your mouth? Lets see your lights, got any pics? I haven't used reflectors yet but I've used lenses and it's easy to clean reflectors.
wietefras
Well-Known Member
Not sure about that stuff for COBs. For HPS it makes some sense to diffuse the light, but for already diffuse enough light like from COBs a direct reflective material would work better I'd think.
Friend of mine tested Orca and it actually didn't do so well. It does have a high reflectance, but light gets reflected in all directions. Which means a significant portion goes up towards the ceiling. So in the end he didn't get more on the plants with it than with other reflective foils. It does make the whole tent look nice and bright though.
On the other hand I also know a HPS grower who loves it. He has his HPS fixtures stuck to ceiling during the whole grow though so that might alter the case (the light coming in at a much steeper angle) and I don't remember what he used before Orca.
Perhaps the white plastic, which is really the worst.
@REALSTYLES, I have tested plenty myself and read many properly conducted tests from other people and/or helped them make sure the test was conducted properly. My lights are in the DIY thread.
All I see you do is scream incoherent/irrelevant nonsense to everybody who even dares to even slightly disagree with you. Not sure where your ridiculous hostility comes from, but I don't really care either.
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