Are reflectors created equal? - Orchid Board

camille1585 · #1 01-30-2012, 04:19 AM

I've decided that instead of splurging on more orchids (also quite difficult to do given the cold), I'll spend that money improving my growing condition. I currently have single 36W and 55W PL lights, but seeing as the collection is growing, I need more lights, and also stronger. PL lights pack more punch than T5s, so I'm going to get a 2 bulb fixture of 55W PL lights. I'm come across two similar fixtures at similar prices. One has a single large reflector for both tubes Here, while the other Here has individual reflectors.

Will I get more even light distribution with one or the other, or does it really not matter?

My other question is about the bulbs themselves. Normally I get Philips or Sylviana bulbs for my yearly bulb change, and have always been happy with them. For the fixtures I linked above they can be sold with bulbs, but they are from a comapny I've never heard of and cost half the price. Now I know that in the world of household CFLs, buying cheap bulbs is a mistake. (turn on slowly, poor light quality...). Is it the same when it comes to growlights? The other thing is that the brand bulbs are only available in 3000 or 4000K, while I can get the cheap ones (on other websites) in 6500K as well. Opinions on this are most welcome!

Ray · #2 01-30-2012, 08:30 AM

All else being the same, the individual-reflector-per-bulb design will distribute the light better to the plants.

Looking at a single, horizontal tube for explanation purposes, only the light from roughly the bottom third goes directly to the plants. The light farther up the sides goes out at such a shallow angle that its intensity is more-or-less completely depleted before reaching anything. Light from halfway up or higher must be reflected back, or is lost altogether.

The "wings" of the reflector - the parts that wrap around the bulb, not the flat part in between - redirect the light from the upper sides of the bulb. If the reflector surrounds both tubes, then the light emitted from the upper sides of the tubes that face each other will not be efficiently reflected downward. (That, by the way, is true with your U-shaped tubes, too.)

msaar · #3 01-30-2012, 10:05 AM

The thing that is not equal is the cost: the individual reflector fixture costs 50% more. Is it worth the 30E difference? Until grow light manufacturers provide light distribution (photometric) data, you won't know for sure.

camille1585 · #4 01-30-2012, 10:32 AM

Thanks Ray, I was hoping to get your input on it! I figured there was some difference, but could get my head around it.

Quote:

Originally Posted by msaar

The thing that is not equal is the cost: the individual reflector fixture costs 50% more. Is it worth the 30E difference? Until grow light manufacturers provide light distribution (photometric) data, you won't know for sure.

The cost difference is not so great actually. The single reflector one does not come with bulbs, while the other one does. Taking the price of bulbs on the same website, they are 7€ each, making the final price difference only around 15€. And the individual reflector one exists in a budget version (nothing covering the ballast mounted on top of the reflector) which is a full 20€ cheaper.
I just gave this website as an example, there are other places that have them a bit cheaper.

Now I'm also wondering if I shouldn't splurge on a 2ft 4 bulb T5 fixture instead (which would give me equal wattage as 2 PL bulbs of similar length), the distribution of light will be much more even, particularily on the edges. My issue is that replacing bulbs is way more expensive than with PL lights since I'd have to change 4 instead 2.

msaar · #5 01-30-2012, 12:31 PM

I can't speak for europe, but in the US, the most economical lamp would be 4' T-5, since that is produced in much greater numbers.

camille1585 · #6 01-30-2012, 12:34 PM

I can hardly find anyplace that sells T5 here! They don't seem to be as widely used as in the US, so naturally the ones I find cost lots of $$$$

camille1585 · #7 01-31-2012, 05:03 AM

I may stick with the cheaper single reflector version (found it for less elsewhere, it's by far the cheapest lighting solution.) Last night I was searching through weed forums for information, since I would consider them experts when it comes to plant lighting. The people who use PL lights seem to have no issues with the single reflector, and the reflector debate doesn't even seem to really pop up, so if it's good enough for weed cuttings and growth, it's good enough for orchids!

skanderson · #8 05-10-2012, 11:31 PM

as a quick answer no not all reflectors are created equal. 2 main factors will effect their efficiency. first the material. you want a high grade aluminum that reflects around 96 percent of the light that hits it. the second important factor is geometry of the reflector. this is why power compact flourescents are not as efficient at t5s. t5s due to their small diameter and shape can have a very efficient reflector wasting very little of the light bouncing back into the bulb. this is not possible with the complex shape of power compact bulbs. their are some very good analysis threads on lighting and reflectors on the reef websites.