What lights do I need

Hi Can anyone tell me what lights I need for 1.5 metre square and 2 metres high room. What wattage and colour will I need and how may lights

Read this. It’s by MacG.

It’s long but very informative.


Basically what it means is there could be detrimental levels of lumens/FLUX/PAR and the chlorophyll can break down and stop working. You will notice potentially two things if you have too much light, one not unlike having too strong of light too early the plant will literally start to pull or shrink away from the light, even if you are controlling the heat, the other thing that will happen is the color will bleach right out of the plant as the chlorophyll is damaged and is not able to be repaired or replaced at the high energy levels the light is producing.

There are ways to potentially increase the ability of the plant and it’s chlorophyll to process more energy, adding CO2 and more nutrients – i.e hydroponics that can increase the nutrient supply and water and the speed of which the plant can deliver these things through the roots to the stems and leaves is one way, however even then this can only increase the total amount of light a plant can take by a small margin more, some things just won’t be able to move fast enough, creating and processing enzymes fast enough and even nutrient and water transportation and the transpiration can only move so fast and the plant will quickly hit that limit and then the plant will start to bleach out.

Because of the way light intensity drops off so quickly with a little distance, the inverse-square law, you will see this when a plant has part of it get too close to a high intensity light in a cooled hood or a High Power LED. You can put a whole lot of lights in a small room and as long as you have some distance from the plant you are going to have a hard time really getting to that intensity because of the inverse-square law. You usually will only see these problems in really really small grow rooms with really really high powered lights that do not contribute a lot of heat, this more easily occurs with LED lights as they produce so little heat.

I guess you won’t see it happen much in a large agricultural grow where the high powered lights might be yards or meters away from the plants at the closest, that crazy inverse-square law again, maybe this is why Latewood is not as familiar with this as a problem and he doesn’t really do LEDs.

would mostly depend on your grow space. I don’tknow about the efficiency of 250 watt vs. 400 watt HID lights and I don’t personally use HPS or MH. I do know that a 600 watt HPS is much more efficient than a 1000 watt HPS, in other words the 600 watt HPS has more Lumens/LUX per watt that the 1000, per watt, the 1000 watt will still have more lumens overall, so ten 600 watt HPS would produce more lumens than six 1000 watt HPS. Also HPS produces more lumens than MH per watt, so say a 400 watt MH would not put out the total LUX as a 400 watt HPS.

Up to a point you can put as much light as you can and still deal with getting rid of the heat. You do have to be aware of photo-inhibition as stated above.

In general minimum amount of lighting needed is around 2000 lumens per square foot.

Optimal is around 5000 lumens to 7000-10,000 or maybe even more, lumens per square foot.

No matter the type of light, if you can find the exact specs for its lumens/FLUX per square foot (or the equivalent PAR for red/blue only LEDs) you can use this as a loose guide as to what you need as minimums:

Seedlings and clones require about 400-1000 lumens per square foot.

Vegetative growth requires about a minimum of 2,000 to 3,000 lumens per square foot.

Flowering requires about 5,000 to 10,000 lumens per square foot, ideally, and can take possibly much more.

10,000 lumens is supposed to be about the average power of the sun at sea level on a clear day at high noon, or something like that, lol.

8,000 - 12,000 lumens is supposed to be about the power of the full sun without any overcast or no clouds.

It’s not ideal, but you can make do with 2,000 lumens for an entire grow if necessary.

do not endorse any name brand, the most credible and reliable name brand LED systems are way over priced right now in my opinion.

The system I started with is not in business anymore and I modified it so much that is now my own custom rig and I do not build them for sale or otherwise, although one could be built from scratch at a fraction of the price of any name brand and maybe even a fraction of the knock off direct from China equivalent models. A good LED system can and will give you amazing results and the best bang for electric bill buck.

LED lights right now have no real good “industry standard”, especially as to how they are marketed and sold. Some companies will give you an accurate “HID wattage” equivalent, but most do not, even some of the really good manufacturers, all they give you is the “theoretical” maximum wattage. For example, if the light is made of 100x3 watt LEDs, then it would be marketed as a 300 watt LED fixture. But it is likely really only running at about 150 watts and it may or it might not even be driven at half power and maybe less than a third, say only 75 watts and may not be putting out the equivalent of a 250 – 300 watt HID light. You are going to have to do a lot of research and some of these answers may not be available, even from some of the more reputable manufacturers.

In general you want to be sure both red, and both blue spectra are covered and a little IR and a little UV.

UV 410 nm and Blues 430nm~440nm and 450nm~460nm, and Reds 620nm~630nm and
645nm~660nm, and IR 850nm

Only about 25% blue is needed for tight internodes and to avoid stretching. Very very little IR and UV is needed at only about 2% each.

And a lot of full spectrum white LEDs are often added, I have added a lot to my own setup mostly just because it makes the light easier on the human eyes, more than performance, full spectrum white light will be rated with the kelvin temperature rating and 2700 Ks are redish “warm white” and 5000-6000 Ks are about perfect/pure/true white and much above 6000, say 6500 K is blue heavy white, often called cool white. More heavy on the blue light for veg and more heavy on red for flower. Most lights will be marketed for veg or bloom or some may be called full spectrum for dual purpose veg and bloom and you will notice the ratio of red vs. blue change for the said light.

These are the loose guides to evaluate the technology, most of the well established name brands follow most of these as guide lines and even among the better companies the exact balance and ratios are not always agreed upon. But if you do some research you can probably find an Apollo or Blue Dog equivalent light for half the price, it even likely comes out of the same assembly line but without the name brand stamped on it. P.S. I only mention these two brands as they are well established, not that they are necessarily any better than some of the other new reliable name brands. California Light Works and Bloom Boss are two other well respected name brands but you will notice all of these tend to be a bit on the pricey side, Apollo might be the most affordable. I personally have no experience with these brands but they do seem to get the highest ratings and recommendations around the web.

I’m very pleased with my LEC.


At 2 meters tall though you’ll probably need more headroom for this light because 18-20" is about as close as you want your tops.
I run it in a 3x3x7 foot Gorilla tent and that is just about perfect. My tent is expandable to 8 feet tall if need be.