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Lighting Types and Intensities Guide Summary:
Successful cultivation requires plenty of knowledge, patience and practice. Here at Greenmans Page, we offer support and advice for growers of all experience levels. In this article, we discuss an often overlooked factor of cultivation – lighting types and intensities.


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.


= 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 luxMin. necessary for life
10000 – 15000 luxMin. necessary for consistent but sparse growth
20000 – 25000 luxMin. necessary for robust growth
25000 – 30000 luxMax. Efficiency for Sub Tropical varieties
25000 – 50000 luxMax. 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)

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:


LumenWattlm/wattKelvinHoursManufacturer, Name
53,000430123.3200016kPhilips, 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 Sourcelumens1.0 m21.5 m22.0 m22.5 m23.0 m23.5 m24.0 m2
1000W HPS1400007000056000467004000035000
600W HPS90000600004500036000300002570022500
400W HPS5000050000333002500020000
250W HPS290002900019300
1000W MH1150005750046000383003290028800
400W MH40000400002670020000

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.



HPS Conversion
LumenWattlm/wattKelvinHoursManufacturer, Name
40,500360112.5190024kPhilips C150S63/RETROLUX
23,000215106.9190024kPhilips C215S65/RETROLUX
15,000150100190024kPhilips C260S64/RETROLUX


High Presssure Sodium (HPS) bulbs
LumenWattlm/wattKelvinHoursManufacturer, Name
1400001000140.0210024000Philips C1000S52 Ceramalux
1300001000130.0210024000Sylvania LU1000 Lumalux
90000600150.0210024000Philips C600S106 Ceramalux
84000600140.0210018000Sylvania LU600 Planta
53000430123.3210016000Philips Son T Agro 430W
51500430119.8210018000Sylvania LU430 Planta
50000400125.0210024000Philips C400S51 Ceramalux
50000400125.0210024000Sylvania LU400 Lumalux
47500360131.9210024000Philips C360S51/EW Ceramalux
29000250116.0210024000Sylvania LU250 Lumalux
28500250114.0210024000Philips C250S50 Ceramalux
27500225122.2210024000Philips C225S50/EW Ceramalux
22000200110.0<210024000Sylvania LU200 Lumalux
16000150106.7<210024000Sylvania LU150 Lumalux
63007090.0<210024000Sylvania LU70 Lumalux



MasterColor (MH)
LumenWattlm/wattKelvinHoursManufacturer, Name
62007088.630007500Philips CDM70/U/M
62007088.630007500Philips CDM70/C/U/M
950010095300010kPhilips CDM100/V/M
920010092300010kPhilips CDM100/C/V/M



Metal Halide (MH) bulbs
LumenWattlm/wattKelvinHoursManufacturer, Name
1250001000125.0420012000Iwasaki MH BSX/BU 1000
1150001000115.0400012000Sylvania MS1000/BU SupMetalarc
1150001000115.0340012000Sylvania MS1000/C/BUSupMetalarc
1110001000125.0370010000Philips MH1000/U/BT37
40000400100.0430020000Philips MS400/HOR
40000400100.0500020000Philips 5K High Output Metal Halide
3900040097.5420020000Sylvania MS400/HOR SupMetalarc
3800040095.0420020000Iwasaki MH 400 Eye Sunlux
3800040095.0380020000SylvaniaMS400/C/HOR SupMetalarc
3450040086.3320020000Sylvania MS400/3K/HOR Super



LumenWattlm/wattKelvinHoursManufacturer, Name
2300025092.0430010000Philips MS250/HOR
2300025092.0420010000Sylvania MS250/HOR SupMetalarc
2200025088.0380010000Sylvania MS250/C/HORSuMetalarc
1800025072.0320010000Sylvania MS250/3K/HOR Super



LumenWattlm/wattKelvinHoursManufacturer, Name
1500017585.7430010000Philips MS175/HOR
1500017585.742007500Sylvania MS175/HOR SupMetalarc
1500017585.738007500Sylvania MS175/C/HORSMetalarc
1500017574.332007500Sylvania MS175/3K/HOR Super



LumenWattlm/wattKelvinHoursManufacturer, Name
930010093.042007500Philips 4K Master Color ED-17
850010085.0320010000Philips MS100/BU/BD/M/3K
780010078.0430010000Philips MH100/U/ED28/HR
680010068.042007500Philips 4K Master Color PAR-38



Flourescent tubes, 48″
LumenWattlm/wattKelvinHoursManufacturer, Name
44006073.3300012000Sylvania F48T12/D830/HODesigner
42506070.8410012000Sylvania F48T12/D41/HO Designer
42506070.8350012000Sylvania F48T12/D35/HO Designer
42506070.8410012000Philips F48T12/SPEC41/HO
42506070.8350012000Philips F48T12/SPEC35/HO
42506070.8300012000Philips F48T12/SPEC30/HO
37004092.5500024000Philips F40/AX50 Advantage X
37004092.5410024000Philips F40/AX41 Advantage X
37004092.5350024000Philips F40/AX35 Advantage X
37004092.5300024000Philips F40/AX35 Advantage X
36004090.0500024000Philips F40T12/ADV50/ALTO
36004090.0410024000Philips F40T12/ADV41/ALTO
36004090.0350024000Philips F40T12/ADV35/ALTO
36004090.0300024000Philips F40T12/ADV30/ALTO
35004087.5410020000GE Staybright
35004087.5350020000GE Staybright
35004087.5300020000GE Staybright
34006056.6650012000Philips F48T12/D/HODaylight
33004082.5300020000Philips F40T12HomeLightWarm
33004082.5410020000Sylvania F40/D841 Desi800
33004082.5350020000Sylvania F40/D835 Desi800
33004082.5300020000Sylvania F40/D830 Desi800
33004082.5410020000Philips F40/41U Ultralume
33004082.5350020000Philips F40/35U Ultralume
33004082.5300020000Philips F40/30U Ultralume
32804082.0500020000Philips F40/50U Ultralume
32004080.0410020000Philips F40T12HomeLightCool
32004080.0350020000Philips F40T12HomeLightWarm
30004075.0650020000Sylvania F40/D865 Design800
23254058.1650020000Philips F40DXDaylightDeluxe
22504056.3500020000GE F40/SUNSunshineFullSp
19004047.5305020000GE F40PL/AQ/WS Plant&Aquarium
18754046.9340020000Sylvania F40GRO/WS Gro-Lux
16004040.0na20000Philips Agro-Lite
8004020.0675020000GE F40PL Gro & Sho



Mercury Vapor bulbs
LumenWattlm/wattKelvinHoursManufacturer, Name
2300040057.5350024000SylvaniaH33GL-400/N Warmtone
2200040055.0430024000SylvaniaH33GL-400/DX BrWhDlx
1300025052.0350024000SylvaniaH37KC-250/N Warmtone
1250025050.0430024000SylvaniaH37KC-250/DX BrWhDlx
890017550.9<350024000SylvaniaH39KC-175/N Warmtone
840017548.0<430024000SylvaniaH39KC-175/DX BrWhDlx
450010045.0<350024000SylvaniaH38JA-100/N Warmtone
410010041.0<430024000SylvaniaH38JA-100/DX BrWhDlx



Tungsten Halogen Quartz double end lamps
LumenWattlm/wattKelvinHoursManufacturer, Name
22000100022.0<32002000Sylvania 1000T3Q/CL
21000100021.0<32003000Philips 1000T3Q/P/CL cl pl
1100050022.0<32002000Sylvania 500T3Q/CL
1050050021.0<32003000Philips500T3Q/P/CL ClPlusline
1000035028.630752000GE Q350T3/CL/ULTRA
920040023.0<32002000Philips 400T3Q/CL Clear
600030020.0<32003000Philips300T3Q/P/CL ClPlusline



Standard Incandescent Bulbs 110V/230V
LumenWattlm/wattKelvinHoursManufacturer, Name
4004010.02000100040 Watt Std. Incandescent Bulb




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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