cfl (compact fluorescent) lighting

[beckdg]

i received a pm about this topic and not only was my answer too lengthy for a single pm, but i though maybe this was a subject that should be shared as well.

so here goes...

been a long time beck, how goes the viv forums?
so i'm looking for some specific info on CFL lights. i tried using the search feature but came up with a lot of unrelated stuff & i figured you could point me in the right direction.
anyway, for the last 8mos or so i've been using 2 6500k daylight CFL's in my naturalistic viv housing a crested gecko. most of the plants have survived, but with minimal actual growth after all that time. so i always heard when using CFL's you need to use a 6500k in conjunction with a 4500k to get a more full spectrum effect. since i also read that fluorescents only produce the correct blah blah for about 6mos i figured it was time to get new ones & might as well get a 4500k while i'm at it.
the problem is i can't find the kelvins listed anywhere on the packaging when i go to the hardware store. another problem is i don't even really understand what all this technical specifications of lights actually mean. lumens, kelvins, light output, color temp. etc.
i guess i'm just looking for suggestions on two CFL's that will be good for my plants.
thanks man-

it's going.

yes i can.

fluorescent by nature = full spectrum. no need for different bulbs unless it pleases your eye. it's not like we're trying to bud, flower or produce a veg state to where we'll need anything more than growing conditions. if we were, we still would change out bulbs for fruiting/flowering instead of run them together anyway.

the 6 month rule is a load of bs with two exceptions...

if dropping intensity by 20-30% puts you in danger of not having enough light to support photosynthesis then you'll have to replace your lights about every 6 months regardless.

the second exception would be uvb or uvc bulbs that can actually burn up the gasses that effectively produce their useful uv light.

lumens = total light output as perceived by the human eye
lux = same thing but measured at a specific distance over a specific area

light output can mean any number of things. it can be watts which is a measure of power, not light. it could be referencing the spectral graph, lux, lumens, pur, par, candle power, etc. ... but usually if it's printed on a package it references the perception of light by the human eye.

color output and cri (color rendering index) are also highly dependent on perception by the human eye.

here... check out the light info posted here... self watering terrarium
(username dundadundun)

also check out the information on cfl's here... PAR Data-Spiral Power Saver Bulbs, lighting question

now, what you're primarily interested in is par (photosynthetically active radiation) or to a lesser extent pur (photosynthetically useable radiation) and how to maximize that with your cfl bulbs. since the main proponent of maximizing your par/pur/output is how well your bulbs are reflected, this is where you're going to want to start, IMO.

for that reason, i'll suggest you look over this thread to get an idea of some practical applications in use... My inexpensive CFL light solution

the basic principle with growing light output is to have your peaks in your spectral graph in the blue and red spectrums closest to your green spectrum dead smack in the middle of the graph, and to have as little of every other color as possible without necessarily completely isolating those two colors by having a flat line with two huge peaks.

so if you're looking at a graph on a package, you want a couple tall camel humps in blue and red near the green. if it looks like a flat line with 2 spikes like a heartbeat monitor, it's not likely great light.

now... back to reflectors... for cfl lights... since the bulbs (tubes) are twisted, one side of the bulb blocks the light put out from the other side of the bulb in the middle of the bulb and if the bulbs are screwed in horizontally and reflected from above, then any light not traveling straight downwards will be reflected straight back at the bulb again blocking the light from passing through. this phenomena is called restrike.

to minimize restrike, the best reflectors for cfl bulbs are dome reflectors like clamp lamps. this allows the light from the bulb to shine outward and away from the bulb before being reflected downward away from the bulb without the bulb itself interfering.

to further maximize your useful light output, the thinner/smaller the bulb (given approximately the same output) the better.

now... of course dome reflectors can be quite large and cumbersome and too large of a reflector minimizes the number of bulbs you can fit into a given area... but too small of a reflector (given the shape the reflector takes to make it small and the direction it winds up reflecting the light) and you're losing light reflecting it straight back at the bulb.

now... i've tried a good wide variety of cfl bulbs, personally. not that i can recall all of them at this point, but i do have a favorite. i prefer ge daylight 6500k cfl's that can be purchased at any walmart. here's what they look like...

[beckdg]

now keep in mind there's not only 40 to 100 watt equivalents, but they also have different size bulbs in the same packaging. if you have the need to maximize your light output, i suggest purchasing the more expensive of the two as they're either going to be t3 or even t2 bulbs. the T number is going to represent how many eigths of an inch thick the bulb itself is going to be, so theres a somewhat significant size difference between bulb size in the different bulbs. less bulb in the way is going to mean more light for you to use.

here's an example...



the bulb on the right is obviously going to have less bulb in the way and thus less restrike. also... notice you can actually see between the swirls so light can get through there as well.

given all this information and my experience with different cfl bulbs, i'd say unless you're going to go to a hydro shop and pick up expensive specialized cfls and even more expensive units to power them, this is what i would suggest for anyone trying to maximize their light output on minimum dollars...

go to walmart and pick yourself up t2 or t3 ge daylight 6500k bulbs...
then peruse over to the hardware section and grab yourself 8 inch dome (clamp) lamps (shaped like half a ball, not like the front of a torpedo).

you certainly could get your lamps elsewhere if you prefer the painted look (typically glossy black on the outside and a reflective ceramic or glossy white interior) but they'll likely be a little costlier.

hope this helps

[Mink]

on the topic of reflectors.

Have you ever incorperated say mylar or panda plastic into the inside of the hood to help reflect light back into the tank?
say with a 3 light t5 setup

[beckdg]

not yet.

i'd be more likely to use either of those as grow room walls than light hood reflectors, though.

[Mink]

I already use panda plastic in a grow room situation, i was just curious if you had incorporated it into a hood yet.

Figure i have some extra so i might as well