The Definitive Lighting Guide

OK, theres a lot of confusion going around about light types, wattage, cool/warm/daylight bulbs, EVERYTHING! I thought I'd make my 420th post a good one and try and stop the confusion. Here we go.

The figures below have four categories:
Hrs [expected globe life in hours],
lms/W [Lumens per watt of bulb power],
K [Kelvin: measure of coolness/warmness - higher is warmer], and
CRI [Colour Rendering Index - How well the colours of items under the bulb will come up].

Incandescent [Tungsten]: [ 750~1k Hrs ][ 16~19 lms/W ][ 2100~3300 K ][ 100 CRI ]

Metal Halide [E17, BT37]: [ 10k~20k Hrs ][ 48~53 lms/W ][ 5300~6500 K ][ 65~75 CRI ]

Flourescent Lighting : [ 6k~15k Hrs ][ 59~65 lms/W ][ 2700~5000 K ][ 82 CRI ]

T5 Flourescent Lighting : [ 20k Hrs ][ 87~96 lms/W ][ 3000~4100 K ][ 82 CRI ]

T8 Flourescent Lighting : [ 20k Hrs ][ 78~92 lms/W ][ 2700~5000 K ][ 75~86 CRI ]

High Pressure Sodium : [ 24k~30k Hrs ][ 76~112 lms/W ][ 1900~2100 K ][ 22 CRI ]

The types above are all suitable for growing, with the exception of incandescent bulbs. Whilst incadescents may be cheap to buy and give out a good spectra for flowering, they are inefficient, give out a lot of heat and have a short life-span. These factors make them totally impractical for growing. Similar problems apply to halogen lights - extreme heat and innapropriate spectra emission are the main ones. Also, don't use blacklights. They give off very unsuitable spectra for growing and produce few lumens. LED technology is something to keep on the lookout for - although it is currently expensive to purchase initially, it outlasts virtually all other artificial light sources and can be had in almost any wavelength which makes it very suitable for a grow. Low individual wattage and penetration are and issue though, and numerous LED's need to be used for effective lighting.

For vegetative growth, you'll want a lighting system up around the 5000 to 6500 Kelvin range. Then, when you want flowering, switch to a secondary system - around 2700 to 3300 [rough figures, allowing leeway for bulb availability and type]. Make sure you can dissipate the heat generated by differing, however. Remember, it doesn't have to be all one type or the other - combinations can be made that include both ends of the spectrum, or only one for a tight-budget grow. Results will obviously not be as good if only using one end of the required spectrum however.

Ideally, you'll be wanting at least 65 watts per square foot of growing area [based on flourescent lighting]. You can decrease your growing area by placing reflectors around the plants, thus optimising your growing conditions. White painted canvas and plyboard as well as plain mylar and styrofoam can all be used for this purpose. Basically, the more light you have the better. For comparison the sun gives around 5000 lumens per square foot on a bright day, with the 65 watts mentioned above giving roughly 4000 lumens per square foot. This might sound ok, but artificial light roughly halves in intensity for every foot it travels, which means you need to have a well penetrating light to start with [MH & HPS] or use side lighting/reflection for best results. Training plants can also be of great potential with this issue.

If you're wondering where the "CRI" rating comes into all this, it pays to keep in mind that objects are not as they appear when under lights of a low CRI. To diagnose any sickness or discolouration when growing under lighting with a low CRI [HPS and to a lesser extent MH], you should ideally switch to another light source for best visual conditions. For example, HPS may dull colours and make them appear much more yellow/orange than you would see under daylight. MH tends to go the other way, making things look bluer than they really are.

Something else to watch out for is lighting system degradation - a standard Metal Halide lamp will depreciate in its lumen output by up to 25% over its life for example. This can be reduced to some extent by using an electronic [digital] ballast, which will improve lumen maintenance by up to 10% for MH and Flourescent systems.

Hope this helps everyone - maybe it could be made a sticky or something...and of course if the info I've supplied is incorrect or I've missed something, feel free to say so [lengthy replies best put to me in a PM].

Cheers all - boingk

 

Hi there everyone, good to see you found the thread & thanks for those who've given me +rep! Its not that Incandescent** bulbs can't be used, but just that you'd need so many of them the heat and power consumption makes it almost impossible [eg: a standard 9000 lumen grow* requires approx 3 x 48 watt CFL, but over 8 to 10+ standard 60 watt incandescents]. Fluorescent lights are around 4 to 5 times more efficient at converting electricity to light, and thus are the better option by far, whilst still being relatively cheap and giving off minimum heat.

CRI rating just tells you not to judge the colour and health of a plant under lights with a low CRI rating, because the colours will not be well represented.

* A 9000 lumen grow assumes you're doing a small personal use grow, with under 1.6 square feet of space with adequately reflective walls and 2 plants of small to medium size [under 30''].

**Incadenscent bulbs are the normal type of lightbulb, with a tungsten filament through which electricity flows to provide light. Generally, all tungsten filament bulbs are relatively inefficient at converting electricity to light. Their pre-runner was invented in 1879[!] by Thomas Edison, with the first practical incadescent filament bulb being made by Edison in 1880. Not a whole lot has changed in their design since then, the basic principle is still the same.

 

As should everyone else! A nice piece of documentation there...good info to know. Wish I could get some of those Phillips red+blue CFL's!

 

DierWolf, thanks for the info - I adjusted the table accordingly. I've never actually seen a MH light [unless you count lamp-posts], so to be honest I'm just going off the info I've been able to scrounge from a few commercial lighting sites and sources. Thanks for reading!

PurpHazey - check the 'Lamp Spectra' link in Spanishfly's signature for info on the red/blue lights. T5's are specialised fluro's, thats about all I know about them unfortunately. I've seen a few threads floating around about them - try the search function. Google may help, as would your local electrical store; if you ask them I'm sure they'd be able to special order some for you. Hope this helps.

 

Yeah, I'm aware of this...but at my college I think they use MH...either that or I've just plain old never seen one in the flesh. Ain't nothin' wrong with that I guess aside from me feeling a bit like an ass, haha. But thats not unusual for me

 

*Bump*

 

*bump*

Just keeping info available for people, cheers all.

 

I'm guessing you mean Fluorescent Tubes and Compact Fluorescents.

You wouldn't be using tubes unless you had a fair few in a room filled with plants, for most people compact fluorescents are the best bet because of their large light output relative to their size. That, and they can fit into a standard socket rather than requiring a sepcial fixture like tubes. The info for fluorescents on there goes for all of them.

For Kelvin, that is the range of light spectrum temeratures that you will get. When I said 'warmer', I meant spectrum-wise. So while CFL's put out a lot of light, their spectrums are generally low unless you buy specialised ones. You'll want something like 5000 to 6500K for growing, and then 2700 to 3300K for budding and flowering. A mix is generally fine.

Alternatively, you could just use 'daylight spectrum' CFL's.

With expected life, this will vary amongst brands and with usage. For example, with the lights turned on non-stop, they will tend to last longer than stated because the starter capacitor is put under less stress. Its the same principle as for regular globes: They always blow at start-up because the current loading is highest and this eventually shorts the wiring, blowing the globe. I've personally seen fluorescent globes last almost 3 years non-stop in a cool-room, which is something like 28,000 hours. They were only rated for 18,000 hours.

Hope that helps - boingk