Best Lighting Types and Intensities for Marijuana Plant

Lumen

A unit of measurement of the total flow of light which is emitted continually from a source. One lumen is equal to the flow of light which is emitted from a very small wax candle.
The common 40 Watt incandescent bulb emits some 400 lm (lumen). So the efficiency of that bulb is 400lm/40Watt= 10 lm/watt.

LUX

= lm/m2, the intensity of light which falls on a surface.

Colour Temperature

– measured in degrees Kelvin, the color of a light’s output in relationship to the degree of heat applied to produce the specified colour of light. Daylight is measured around 5000 degrees kelvin

If we direct all light from our 40 Watt lamp towards a floor area of 1 square meter the intensity of light on that area will be 400 lux, (400 lumen distributed over 1 square meter, 400/1 lm/m2 = 400 lux,) which is a little better than moonlight, but far away from the sunlight intensities we need for growing plants.

The sun gives some 50 000 lm/m2 = 50 000 lux at the earth surface on a clear summerday. See the table below.

The 40 Watt incandescent lamp is not only too weak for growing plants, it also has too little blue in its spectrum and is far too inefficient. Fluoroscent tubes and HPS and MH lamps are the better choices.

Cannabis needs 24 hours of strong light for the first 4-6 weeks of vegetative growth. Then it needs 2 months of 12/12 hours of strong light and very dark, to flower and ripen. If they get less than 30000 lux they will still grow vegetatively but slower. And they will flower less, if at all.

 

Light Requirements of “High Energy” Plants
1000 – 5000 lux	Min. necessary for life
10000 – 15000 lux	Min. necessary for consistent but sparse growth
20000 – 25000 lux	Min. necessary for robust growth
25000 – 30000 lux	Max. Efficiency for Sub Tropical varieties
25000 – 50000 lux	Max. Efficiency for Equatorial varieties

 

Plants need 25000-50000 lux too grow fast.

90000 lux Max. Sunlight Intensity on Earth’s surface. This is too much light, it is not good for the plant.

Plants subject to intensities at this level or greater are at risk of “solarization,” whereby photosynthesis is retarded. This can happen at noon on a clear Tropical summer day, especially at high altitudes.

140000 lux Sunlight above atmosphere (Solar Constant)

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More advanced theory: Scientific, but has many answers about how and why.

Air Temperatures between 23C (70F) and 32C (90F) are ideal for growth; beyond 35C (95F) can adversely affect plants, retarding photosynthesis, and, in extreme cases, can cause leaf burn if a radiant heat source is nearby.

Calculating with lumen, lux and efficiency:

The cheapest and easiest solution to the beginner is to use fluoroscent tubes. The usual ones are 120 cm (48″) long, and give at best 4000 lumen.

*****Ed Note: If you care to get a light meter and measure the light from various distances to your flouros, you’ll see immediately that you will want to keep the lights as close to the top of your plants as possible. *****

Your grow room must have at least these dimensions: 140 cm high (these plants get big, 180 cm is better, 120 cm long (to accomodate for the tubes), and wide enough, let’s say 60cm (2 feet). The easiest is to build an extra wall, made of silver tarpaulin or wood. This wall is placed 60 cm from a real wall, to create a space of say 200*260*60cm for use as a greenhouse or rather two. Build the wall and divide the space up into two small rooms. Make some type of opening, so you can take care of your plants later. Put in ventilation and cover all inside surfaces with al-foil using a stapler. We want the light to bounce around in there until it finds a green leaf to do its work in. As much light as possible is needed for the growth of the plants. The ventilation consists of a 12Volt fan which pushes the warm air from the green house through a plastic tube which ends outside the house to let the warm moist and odors out. Instead of a fake wall you can disguise the green house as a very big bass speaker, stereo wall, tv-stand, cupboard or whatever.

Buy the fluoros in ready-made units or do it yourself like this:

Buy the bare necessities to put up fluoros, that is reactors, lighters, tube holders, lighter holders, wire.7mm, capacitors and connectors.

Most of these devices have pushcontacts, that means you don’t have to solder or screw much, just strip off the insulation from the cable and push it in.

Put up as many tubes as possible in the ceiling of the green house. You might be able to get 6 tubes into every green house half. Every green house has a floor area of 0.60m*1.30m=0.78m2 With 6*4000 lumen you get 24000lumen. Divide by 24000lm with 0.78m2 to get 31000 lux, which is good enough.

Use hanging mounts for the tubes, they are cheapest and easiest to use. They also make it easier to pack the tubes densely in the cieling or hanging at different levels, hanging only in the thin electric cables. If you manage to get 10 tubes into the top of the green house you get 40000lm/0.78m2= 51300 lux in there.

As another example, let’s take one of the most popular hps grow bulbs:

 

Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
53,000	430	123.3	2000	16k	Philips, SON T AGRO

 

The Son-T-Agro gives out 53000 lumen. If we use a reflector to direct all of that light towards a floor area of 2 m2 we get a light intensity on that area of 53000 lumen/2 m2, which is 26500 lumen/m2 (=lux)

We can see in table 3 above that it fits in: “25000 – 30000 lux =Max. Efficiency for Sub Tropical varieties”.

We add some daylight fluoros, 6 fluoros a 4000 lumen=24000 lumen. Divide by floor area 2 m2 to get =12000lumen/m2=12000lux

Together the hps and the fluoros give 26500+12000=38500lux in the 2 m2 big grow room. see table 3: 25000 – 50000 lux Max. Efficiency for Equatorial varieties.

This combination will draw 430Watt+6*40Watt+100Watt in the ballast units, total =530+240=770Watt of electricity.

Our total efficiency is 53 000 + 24 000 lm divided with 770 Watt, which is 77 000 lumen /770 Watt = 100 lm/Watt

At 38500 lux we have an illumination which is optimal for growth,

Illumination Chart

Light Intensity (lux) as a Function of Area Illuminated (m2)
Light Source	lumens	1.0 m2	1.5 m2	2.0 m2	2.5 m2	3.0 m2	3.5 m2	4.0 m2
1000W HPS	140000	—	—	70000	56000	46700	40000	35000
600W HPS	90000	—	60000	45000	36000	30000	25700	22500
400W HPS	50000	50000	33300	25000	20000	—	—	—
250W HPS	29000	29000	19300	—	—	—	—	—
1000W MH	115000	—	—	57500	46000	38300	32900	28800
400W MH	40000	40000	26700	20000	—	—	—	—

For example, from this chart we can see that a 600W HPS used to illuminate an area of 2.5 m2 will result in a lighting intensity of 36000 lux. Note that this presumes that a reflector is being used so that all the light is being directed towards this 2.5 m2 area.

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LIGHT BULB PRODUCT LIST

HPS Conversion
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
40,500	360	112.5	1900	24k	Philips C150S63/RETROLUX
23,000	215	106.9	1900	24k	Philips C215S65/RETROLUX
15,000	150	100	1900	24k	Philips C260S64/RETROLUX

 

High Presssure Sodium (HPS) bulbs
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
140000	1000	140.0	2100	24000	Philips C1000S52 Ceramalux
130000	1000	130.0	2100	24000	Sylvania LU1000 Lumalux
130000	940	138.3	2100	24000	IwasakiEyeSunluxUltraAceMHcnv)
90000	600	150.0	2100	24000	Philips C600S106 Ceramalux
84000	600	140.0	2100	18000	Sylvania LU600 Planta
53000	430	123.3	2100	16000	Philips Son T Agro 430W
51500	430	119.8	2100	18000	Sylvania LU430 Planta
50000	400	125.0	2100	24000	Philips C400S51 Ceramalux
50000	400	125.0	2100	24000	Sylvania LU400 Lumalux
47500	360	131.9	2100	24000	Philips C360S51/EW Ceramalux
45000	360	125.0	2100	24000	IwasakiEyeSunluxUltraAceMHcnv)
29000	250	116.0	2100	24000	Sylvania LU250 Lumalux
28500	250	114.0	2100	24000	Philips C250S50 Ceramalux
27500	225	122.2	2100	24000	Philips C225S50/EW Ceramalux
22000	200	110.0	<2100	24000	Sylvania LU200 Lumalux
16000	150	106.7	<2100	24000	Sylvania LU150 Lumalux
6300	70	90.0	<2100	24000	Sylvania LU70 Lumalux

 

 

MasterColor (MH)
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
6200	70	88.6	3000	7500	Philips CDM70/U/M
6200	70	88.6	3000	7500	Philips CDM70/C/U/M
9500	100	95	3000	10k	Philips CDM100/V/M
9200	100	92	3000	10k	Philips CDM100/C/V/M

 

 

Metal Halide (MH) bulbs
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
125000	1000	125.0	4200	12000	Iwasaki MH BSX/BU 1000
115000	1000	115.0	4000	12000	Sylvania MS1000/BU SupMetalarc
115000	1000	115.0	3400	12000	Sylvania MS1000/C/BUSupMetalarc
111000	1000	125.0	3700	10000	Philips MH1000/U/BT37
40000	400	100.0	4300	20000	Philips MS400/HOR
40000	400	100.0	5000	20000	Philips 5K High Output Metal Halide
39000	400	97.5	4200	20000	Sylvania MS400/HOR SupMetalarc
38000	400	95.0	4200	20000	Iwasaki MH 400 Eye Sunlux
38000	400	95.0	3800	20000	SylvaniaMS400/C/HOR SupMetalarc
34500	400	86.3	3200	20000	Sylvania MS400/3K/HOR Super

 

 

Metalarc
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
23000	250	92.0	4300	10000	Philips MS250/HOR
23000	250	92.0	4200	10000	Sylvania MS250/HOR SupMetalarc
22000	250	88.0	3800	10000	Sylvania MS250/C/HORSuMetalarc
18000	250	72.0	3200	10000	Sylvania MS250/3K/HOR Super

 

 

Metalarc
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
15000	175	85.7	4300	10000	Philips MS175/HOR
15000	175	85.7	4200	7500	Sylvania MS175/HOR SupMetalarc
15000	175	85.7	3800	7500	Sylvania MS175/C/HORSMetalarc
15000	175	74.3	3200	7500	Sylvania MS175/3K/HOR Super

 

 

Metalarc
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
9300	100	93.0	4200	7500	Philips 4K Master Color ED-17
8500	100	85.0	3200	10000	Philips MS100/BU/BD/M/3K
7800	100	78.0	4300	10000	Philips MH100/U/ED28/HR
6800	100	68.0	4200	7500	Philips 4K Master Color PAR-38

 

 

Flourescent tubes, 48″
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
4400	60	73.3	3000	12000	Sylvania F48T12/D830/HODesigner
4250	60	70.8	4100	12000	Sylvania F48T12/D41/HO Designer
4250	60	70.8	3500	12000	Sylvania F48T12/D35/HO Designer
4250	60	70.8	4100	12000	Philips F48T12/SPEC41/HO
4250	60	70.8	3500	12000	Philips F48T12/SPEC35/HO
4250	60	70.8	3000	12000	Philips F48T12/SPEC30/HO
3700	40	92.5	5000	24000	Philips F40/AX50 Advantage X
3700	40	92.5	4100	24000	Philips F40/AX41 Advantage X
3700	40	92.5	3500	24000	Philips F40/AX35 Advantage X
3700	40	92.5	3000	24000	Philips F40/AX35 Advantage X
3600	40	90.0	5000	24000	Philips F40T12/ADV50/ALTO
3600	40	90.0	4100	24000	Philips F40T12/ADV41/ALTO
3600	40	90.0	3500	24000	Philips F40T12/ADV35/ALTO
3600	40	90.0	3000	24000	Philips F40T12/ADV30/ALTO
3500	40	87.5	4100	20000	GE Staybright
3500	40	87.5	3500	20000	GE Staybright
3500	40	87.5	3000	20000	GE Staybright
3400	60	56.6	6500	12000	Philips F48T12/D/HODaylight
3300	40	82.5	3000	20000	Philips F40T12HomeLightWarm
3300	40	82.5	4100	20000	Sylvania F40/D841 Desi800
3300	40	82.5	3500	20000	Sylvania F40/D835 Desi800
3300	40	82.5	3000	20000	Sylvania F40/D830 Desi800
3300	40	82.5	4100	20000	Philips F40/41U Ultralume
3300	40	82.5	3500	20000	Philips F40/35U Ultralume
3300	40	82.5	3000	20000	Philips F40/30U Ultralume
3280	40	82.0	5000	20000	Philips F40/50U Ultralume
3200	40	80.0	4100	20000	Philips F40T12HomeLightCool
3200	40	80.0	3500	20000	Philips F40T12HomeLightWarm
3000	40	75.0	6500	20000	Sylvania F40/D865 Design800
2325	40	58.1	6500	20000	Philips F40DXDaylightDeluxe
2250	40	56.3	5000	20000	GE F40/SUNSunshineFullSp
1900	40	47.5	3050	20000	GE F40PL/AQ/WS Plant&Aquarium
1875	40	46.9	3400	20000	Sylvania F40GRO/WS Gro-Lux
1600	40	40.0	na	20000	Philips Agro-Lite
800	40	20.0	6750	20000	GE F40PL Gro & Sho

 

 

Mercury Vapor bulbs
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
60500	1000	60.5	4300	24000	SylvaniaH36GW-1000/DXBrWhDlx
23000	400	57.5	3500	24000	SylvaniaH33GL-400/N Warmtone
22000	400	55.0	4300	24000	SylvaniaH33GL-400/DX BrWhDlx
13000	250	52.0	3500	24000	SylvaniaH37KC-250/N Warmtone
12500	250	50.0	4300	24000	SylvaniaH37KC-250/DX BrWhDlx
8900	175	50.9	<3500	24000	SylvaniaH39KC-175/N Warmtone
8400	175	48.0	<4300	24000	SylvaniaH39KC-175/DX BrWhDlx
4500	100	45.0	<3500	24000	SylvaniaH38JA-100/N Warmtone
4100	100	41.0	<4300	24000	SylvaniaH38JA-100/DX BrWhDlx

 

 

Tungsten Halogen Quartz double end lamps
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
22000	1000	22.0	<3200	2000	Sylvania 1000T3Q/CL
21000	1000	21.0	<3200	3000	Philips 1000T3Q/P/CL cl pl
11000	500	22.0	<3200	2000	Sylvania 500T3Q/CL
10500	500	21.0	<3200	3000	Philips500T3Q/P/CL ClPlusline
10000	350	28.6	3075	2000	GE Q350T3/CL/ULTRA
9200	400	23.0	<3200	2000	Philips 400T3Q/CL Clear
6000	300	20.0	<3200	3000	Philips300T3Q/P/CL ClPlusline

 

 

Standard Incandescent Bulbs 110V/230V
Lumen	Watt	lm/watt	Kelvin	Hours	Manufacturer, Name
400	40	10.0	2000	1000	40 Watt Std. Incandescent Bulb

 

 

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Equivalences:

1 lm/m2 (lumens per square meter)

= 1 lux (lx)
= 10-4 lm/cm2
= 10-4 phot (ph)
= 0.093 lm/ft2
= 0.093 foot-candles (fc)

1 meter = 3.3 feet

1 square meter = 10.8 square feet

1 foot = 0.3 meter

3 feet = 1 yard = 0.91 meter

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