Lumens per square foot

Hey all,

I have a quick question. In OG a few years back I found a post that some cat had done about light requirements. I am helping a friend getting started and he wanted mr to find it for him. Naturally I said sure. Now I can't find the post. Dammat!!!

Any help would be very much appreciated. Lumens per square foot?

BriarPatch

I'm not exactly sure why your asking ICmag to find something at Overgrow for you, but regardless, what would you like to know about lumens per square foot? I'm sure thee are enough knowledgable people around here to direct you.

Cap

I use 6100 lumens per sq. foot during flowering with very good results. Many people use less and get by okay.

{post that I was responding too was deleted. Don't ask me why}

No offense cashcrop, but "big n' tiggt nugzz" is important because of what? 5000 lumens is the minimum? In whose experience? I run my room at around 2000 lumens psf and have regularly hit .75 grams per watt. I have colas that weigh 5-7 grams dry. Does that qualify as "big n' tight"? If not, what does?

Fluorescent Lights

These are the most common and least expensive lights that gardeners can use to grow plants. They are more efficient than common incandescent lights for plant growth, giving more light per watt of electricity with less heat. By virtue of their light quality and cool operating temperature, they are by far the preferred way to establish seedlings.

Fluorescent lights work in two steps. First, electrons stream between electrodes at each end of the tube and produce ultraviolet light, which is in turn absorbed by phosphors coating the tube's inner wall. Those phosphors (substances that emit light when excited by radiation) convert and reradiate the ultraviolet light as visible light. The mix of phosphors determines the color of the light produced.

Fluorescent tubes range in power from 15 to 215 watts, but high wattage tubes are increasingly rare. Most useful for indoor gardeners is the 4-foot-long 40-watt "bipin" tube, with two contact points at each end. In general, the cost of a tube varies according to how common it is. For instance, a 4-foot cool or warm white tube costs as little as $2, while a specialty full-spectrum tube for plants costs about $20.

Tubes' useful lifetimes are surprisingly variable, ranging anywhere from 12,000 hours (about 18 months) to 34,000 hours (almost four years). Usually the least expensive cool white tubes are the shortest-lived. If maximum intensity is critical, replace tubes before they burn out, at about 70 percent of their rated life. At that point, most tubes are producing about 15 percent less light than when new. According to this schedule, you should replace a tube rated at 20,000 hours and used 14 hours a day after 33 months.

The cost of electricity is easy to calculate if you know how much your local utility charges per kilowatt-hour. Four 40-watt tubes operating for 13 hours consume about 2 kilowatt-hours of electricity.

Color Choices

Fluorescent tubes vary in the color of light they produce. If you've ever experimented with a prism, you know that white-appearing sunlight is actually a combination of colors from violet to red. While some artificial light approaches the color of sunlight, none duplicates it. In all cases, lights produce more or less of certain specific colors.

On the other hand, plants don't need every color in sunlight to grow and flower. For instance, the fact that plants are green means they are reflecting and not using most of the green wavelengths in light. Plants mostly use wavelengths at the two ends of the visible spectrum: the blue end for foliage growth and the red end for flowering.

The earliest fluorescent tubes are now called cool white. These produce an abundance of light in the blue range, but insufficient red light. The so-called warm white tubes complement them by producing more red light.

For many plants, a combination of cool white and warm white tubes will produce good growth. But seedlings need bright light as soon as they germinate, including red and infrared light. Since not enough of this light is produced by either cool or warm white tubes, you'll need to provide supplemental light either from a nearby window or, more conveniently, with fluorescent tubes especially designed for plant growth.

Many different colors of tubes are available. Some are designed to produce specific colors of light, some to approximate sunlight. The color of fluorescent tubes is measured in two ways: color rendering index (CRI) and degrees Kelvin ( o K). CRI is a percentage number that measures how closely the light approximates natural sunlight. Tubes with a CRI greater than 90 are considered to be full spectrum.

The color of light is also measured on the Kelvin temperature scale, and this measurement is called the color temperature. Light that is rich in red has a low reading in degrees Kelvin, and light rich in blue has a much higher color temperature. Ordinary incandescent light bulbs produce light of about 2,800 degrees K, while daylight, which is rich in rays from the blue end of the spectrum, has typical readings from 5,000 degrees to 7,000 degrees K. Fluorescent lights range in color temperature from about 2,700 degrees to 6,500 degrees K. A typical warm white tube is about 3,000 degrees K, while a full spectrum tube is over 5,000 degrees K.

Light Intensity

It stands to reason that brighter lights deliver more energy to plants than less bright ones. But while most fluorescent lights appear to be about equally bright, here again careful measurements reveal many differences.

For gardeners, the most basic and generally most useful measurement of light intensity is a simple calculation of watts of fluorescent light per square foot.

Experiments and tests have demonstrated that most vegetables and flowering plants need 25 to 30 fluorescent light watts per square foot. Houseplants and seedlings do well with 15 to 20 watts, and germinating seeds need the least 10 to 15 watts per square foot.

A standard 4-foot-long 40-watt fluorescent tube provides 10 lamp watts per square foot. Two 40-watt tubes 6 inches apart supply double that amount.

From this standpoint, the most important choice about intensity is how many tubes your fixture supports. Assuming that most fixtures are about a foot wide or slightly wider, the intensity of light from one that holds four tubes (40 lamp watts per square foot) will be double one that holds two tubes (20 lamp watts).

The light intensity of fluorescent tubes is also measured and rated on another standardized scale called lumens. In short, lumens are a measure of the brightness of the emitted light. When it comes to growing plants, brighter--more lumens--is better.

You can measure the amount of light yourself by using various kinds of meters. Meters made for gardeners measure light directly in footcandles. Footcandles are a measure of the light that is reflected from a surface 1 foot away. One footcandle equals 1 lumen per square foot.

You can also use the light meter in your automatic camera: set the film speed to 100 and the shutter speed to f4. Place a matt white card where the plants will be. With the lens focused on the card only, note the shutter speed. If it indicates 1/250, you have about 250 footcandles, 1/500 equals about 500 footcandles, and so on.

The light that fluorescent tubes produce diminishes rapidly over distance. For instance, 6 inches below two 40-watt cool white tubes, light intensity is about 700 footcandles.

Seedlings grow best with higher light intensity, so lights should be 2 to 3 inches above them, close enough to deliver about 1,000 footcandles to the leaves. With insufficient light, they will stretch out and perhaps topple. Leave the lights on for 14 to 16 hours a day. A similar schedule works best for most plants.

Disposal of Used Tubes

Fluorescent tubes contain mercury, which the EPA classes as a hazardous material. However, current EPA regulations neither list nor exclude the tubes themselves as hazardous waste. It is considered safe to dispose of fluorescent tubes in any municipal solid waste landfill. Fluorescent lamp ballasts made before 1979 likely contain PCBs, a family of chemicals widely used until they were banned in the late 1970s. Unless the ballast is specifically labeled "no PCBs," you should assume it does contain them and only dispose of it at approved recycling centers.

AMPERE (AMP) - The unit used to measure the strength of an electric current.

ARC - The luminous discharger of electricity between two electrodes and HID lighting.

ARC DISCHARGE - A transfer of electricity across two electrodes (anode and cathode) characterized by high electrode current densities and a low voltage drop at the electrode.

ARC TUBE - The enclosure, which contains the luminous gases and also houses the arc.

BALLAST - An auxiliary piece of equipment designed to start and to properly control the flow of power to gas discharge light sources such as fluorescent and high intensity discharge lamps. In metal halide systems, it is composed of the transformer, capacitor and connecting wiring; sodium systems require an igniter in addition to the transformer and capacitor.

BU - An industry code indicating that the bulb is to be operated only in a base-up position.

CONVERSION BULB - A bulb of a certain spectrum type specially designed to operate while used in the fixture/ballast of a different type. The most popular conversion bulbs by far are sodium conversion bulbs, which allow one to have the sodium spectrum while still using a metal halide system.

DOME - The portion of an HID outer bulb located opposite base (the neck and threads).

DOME SUPPORT - The spring-like brackets which mount the arc tube within the outer envelope (bulb).

DISCHARGE LAMP - A lamp that produces light by discharging an electric arc through a mixture of gases and gaseous metals.

ELECTRODES - Filaments located at either end of a discharge lamp that maintain an electrical arc between them. See arc discharge.

FIXTURE - The electrical fitting used to contain the electric components of a lighting system.

FLUORESCENT LAMP - A discharge lamp in which a phosphor coating transforms ultraviolet energy into visible light. Fluorescent lamps are good for starting seedlings and rooting cuttings, but do not have enough intensity to sustain aggressive growth in plants in the later stages of life and are not efficient enough in their conversion of electrical poser to lumens of light output.

FOOT-CANDLE - A standard measurement of light intensity, representing the amount of luminance on a surface one foot square on which there is a uniformly distributed flux of one lumen. More simply, one foot-candle of luminance is equal to the light emitted by one candle at a distance of one foot.

FREQUENCY - The number of waves or cycles of electromagnetic radiation per second, usually measured in Hertz (Hz).

HALOGEN LAMP - A short name for the tungsten-halogen lamp. Halogen lamps are high pressure incandescent lamps containing halogen gases such as iodine or bromine which allows the filaments to be operated at higher temperatures and higher efficacies.

HID - The popular acronym for High Intensity Discharge.

HIGH INTENSITY DISCHARGE (HID) LAMP - A general term for mercury, metal halide and high pressure sodium lamps. HID lamps contain compact arc tubes which enclose various gases and metal salts operating at relatively high pressure and temperatures.

HIGH PRESSURE SODIUM (HPS) LAMP - High pressure sodium lamps operate by igniting sodium, mercury and xenon gases within a sealed ceramic arc tube. Sodium lamps emit light energy in the yellow/red/orange regions of the spectrum; the red spectrum stimulates flowering and fruit production.

HOOD - The reflective cover used in conjunction with an HID lamps. The more reflectivity a hood can provide, the more effective it is.

HOT SPOT - The area immediately under an HID lamp where the light intensity is strongest. Hot spots cause uneven growth, but can be remedied by using light movers.

HOT START TIME - The length of time required to bring an HID lamp to 90% light output after a short power interruption.

IGNITER - A component of the ballast necessary for the starting of the bulb in sodium systems.

LUMINANCE - The density of incident luminous flux on a surface; luminance is the standard metric for lighting levels, and is measured in lux (lx) or foot-candles (fc).

ILLUMINATION - The act of illuminating or state of being illuminated. This term is often used incorrectly in place of the term luminance to denote the density of luminous flux on a surface.

INCANDESCENT LAMP - A light source which generates light utilizing a thin filament wire (usually of tungsten) heated to white heat by an electric current passing through it. Incandescent lamps are the most familiar type of light source, with countless application in homes, stores and other commercial settings. Light is produced by passing electric current through a thin wire filament, usually tungsten. Incandescent lamps are totally ineffective as grow lights; they have very limited spectrum, are very inefficient in their conversion of electrical power to lumens of light output (lumen-to-watt ratio).

INTENSITY - A term referring to the magnitude of light energy per unit; light intensity diminishes evenly as you get further from the source.

KELVIN TEMPERATURE (K) - The unit of measurement to express the color (spectrum) of light emitted by a lamp; the absolute temperature of a blackbody radiator having a chromaticity equal to that of the light source (see correlated color temperature). A standard clear metal halide HID lamp has an average Kelvin temperature rating of 4,000K.

KILOWATT (kW) - A unit of electric power usage equal to 1,000 watts.

LAMP - An electrically energized source of light, commonly called a bulb or tube.

LAMP LIFE - A measure of lamp performance, as measured in median hours of burning time under ANSI test conditions.

LAMP LUMEN DEPRECIATION (LLD) - The decrease over time of lamp lumen output, caused y bulb wall blackening, phosphor exhaustion, filament depreciation and other factors.

LAMP STARTING - Term used to describe a discharge lamp's starting characteristics in terms of time to come to full output, flicker, etc.

LIGHT - Radiant energy which can be seen by the human eye. The term generally applied to the visible energy from a source. Light is usually measured in lumens or candlepower. When light strikes a surface, it is either absorbed, reflected or transmitted. Visible light is measured in lumens.

LIGHT MOVER - A motorized device which moves an HID lamp back and forth across the ceiling of a grow room to provide more even distribution of the light.

LUMEN - A measurement of light output; refers to the amount of light emitted by one candle that falls on one square foot of surface located at a distance of one foot from the candle.

LUMINARIES - A complete lighting unit consisting of a lamp or lamps together with the components required to distribute the light, position the lamps and connect the lamps to a power supply. Often referred to as a "fixture".

LUX - A standard unit of luminance. One lux is equal to one lumen per square meter.

METAL HALIDE LAMP - A high-intensity-discharge lamp in which the light is produced by arcing electricity through a mixture of metal halides. The light produced by metal halide lamps is in the white blue spectrum, which encourages vegetative growth and "bushiness" while discouraging upward growth. This is the bulb to use in the first, vegetative phase of plant growth.

PARABOLIC REFLECTOR - A lighting distribution control device that is designed to redirect the light from an HID lamp in a specific direction. In most applications, thee parabolic device directs light down and away from the direct glare zone.

PHOTOPERIOD - The relative periods of light and dark periods within a 24-hour period. Also referred to as day length.

PHOTOSYNTHESIS - The growth process by which plants build chemical compounds (carbohydrates) from light energy, water and CO2

PHOTOTROPISM - The gravitation of a plant part toward a light source.

REFLECTOR - The term sometimes used to refer to the reflective hood of an HID lamp.

REFLECTIVITY - The measure of the reflective quality of a surface; the relative ability of a given surface to reflect light away from it without absorbing, diffusing or otherwise compromising the light's quality, intensity and spectrum.

SOCKET - The threaded, wired receptacle that an HID bulb screws into.

SODIUM LAMP (HIGH-PRESSURE SODIUM LAMP) - High pressure sodium lamps operate by igniting sodium, mercury and xenon gases within a sealed ceramic arc tube. Sodium lamps emit light energy in the yellow/red/orange regions of the spectrum; the red spectrum stimulates flowering and fruit production. Many indoor gardeners switch to sodium lamps when it is time to induce flowering or fruiting of their plants.

SON AGRO - A sodium bulb which, according to the manufacturer, produces 30% more blue light than standard sodium bulbs. The 430 watt SON AGRO also emits 6% more light than the standard 400 watt sodium lamp.

SECULAR REFLECTION - The redirection of incident light without diffusion at an angle that is equal to and in the same plane as the angle of incidence.

TRANSFORMER - The component in the ballast that transforms electric current from one voltage to another.

U (for Universal) - An industry code indicating that the bulb can be operated in any position; horizontal, vertical (base up) or any other.

ULTRAVIOLET (UV) LIGHT - The spring-like brackets which mount the arc tube within the outer envelope (bulb).

WATT (W) - A unit used to measure electric power.

Light Requirements

Light requirements vary by variety. During the growth cycle, most varieties will do well with 1000-1500 lumens per square foot although the plants can use more lumens, up to 3000, efficiently. Equatorial varieties may develop long internodes (spaces on the stem between the leaves) when grown under less that bright conditions. During flowering, indica varieties can mature well on 2000 lumens. Equatorial varieties require 2500-5000 lumens. Indica-sativa F1 (first generation) hybrids usually do well on 2500- 3000 lumens.

Caprichoso said:

No offense cashcrop, but "big n' tiggt nugzz" is important because of what? 5000 lumens is the minimum? In whose experience? I run my room at around 2000 lumens psf and have regularly hit .75 grams per watt. I have colas that weigh 5-7 grams dry. Does that qualify as "big n' tight"? If not, what does?

Click to expand...

I stand corrected. I'm sorry. I deleted the post so no one listens to my misinformation. I've never used less than 5000 psf.. so i guess i wouldn't know about light lower than that. I just posted my opinion based on the my own experience, research i've done and the threads i've read. I'm sure caprichoso knows way more than me so i would go with what ever he says. Maybe i'll stick with obtaining information instead of giving it out from now on.


oh, and i don't mind being corrected... but i sure as hell don't like being mocked or made fun of that much though...but hey, i'm sure you didn't mean it that way.

I do believe I started out chasing the lumen's per sq ft year's ago. Back then what I followed as a grow guide said this, minimum was 5,000 lumen's per sq ft, 5,500 being better, no reason to go over 6,000 lumen's per sq ft. This is a required amount regardless of flurescent or HID lighting.

I have just went of watt's per sq ft with my hps lamp's, and have grown at 35 watt's, 50 watt's, 65 watt's, and even higher watt's per sq ft to see the out come.

Bud per watt, it is strange, but that 35 watt per sq ft cylinder grow actually produced more then 50 or 60 watt's per sq ft in a typical scrog grow. So you see one can get by with less light per sq ft in a vertical grow compared to a horizontal garden, as most vertical grow's do not use a reflector or hood so more light is recieved by the plant's.

For flowering the key to shoot for is 5,000 lumen's per sq ft as a minimum and I personally feel it work's damn good for the return I get.

I noticed another posted some nice info of the flurescent lighting, very nice info and thank you for that, many ask about it and you wrote it so nicely and informative.

Currently my flower room push's 74.28 watt's per sq ft, will I thought I could give the lumen's per sq ft, but my GroLux bulb package's are infomationless, so if memorey is correct, 58,000 lumen's per 600 watt grolux bulb, so if just the 3 600's were used than it would be just at 4,971.42 lumen's per sq ft, but I also have two 400's used on the area, so I push betwen 5000 to 6000 lumen's per sq ft.

I do believe you have gotten all the help you needed.

stay safe and grow the same way

realhigh.

Another idiot who thinks 5000 is the minimum...geez people are stupid...
(jokin real high)

Why delete your post? It makes my response to you look ridiculous. Next time, remove the text and leave the post in place. You wrote it, others responded, your responsibility to the discussion is to keep the continuity of the thread intact.

Where did I call you idiot or stupid? I even prefaced my response with "no offense" and I meant it.

Realhigh makes some good points based on individual experience. I did too. We both have proof to back it up. Perhaps you would like to make a post with those traits as well.

Cashcrop, read all what I have said. I have grown with 33.33 watt's per sq ft in a vertical cylinder I designed, this calculates to 4583.33 lumens per sq ft, and it did better than my flat screen at near 66.66 watt's per sq ft.which was 9166.66 Lpsf., but the self standing grow unit did have a flaw or two, and those can be worked out if I care to do it.

I took and wanted to see what limits in yield planter size would cause, and this has lead me to discover it is a limiting factor to high yeilds and I hope to prove it by increasing the area of the root zone, same method and strain in the same room, and in the end the yields will tell me if I am correct. ( In all right's I knew this as DWC gave me top yeild's, root zone had alot of area to swim in, LOL)

Lower liight level's gave me bud, and some time's alot of it, but quality was down a bit from what I wanted, as grow's went by and I did different thing's, well all lead to more light over the area and the quality got better in the end.

I do what I do for what I get in the end, and this I do love and enjoy.

stay safe and grow the same way.

realhigh.

I am only out to better myself and out do myself and that is all.

I would think that watts/sf is more of a necessity to know than lumens/sf. I think without actually measuring at the surface in question we can only go by the manfacturers data. Not always the best source of accurate information, I think. A light meter is needed for this information.

I designed my grow space based on watts/sf as that gave me more of a standard approach to equipment requirements and comparsions.

I run a 400w hps in a 2x4 cabinet, and I get a decent hafvest contsantly. I also use organic aeroponics and have good success there as well. I veg using both 125w cfls and 4' argosun fluro's. different stations.

I think just as important is the development of roots and their ability to uptake nutrients as the amount and levels of light for the leaves.

Avid

Cultivation Bible said:

To determine how many lumens per square foot you have: Find out the square footage of your space. Width x Depth = Square feet. Divide the lumens available by your square footage. This will give you lumens per square foot. Example: Say your space is 3 feet deep by 4 feet wide, 12 square feet. The total lumens available from your light(s) is 45000 lumens. 45000/12 = 3750 lumens per square foot.

Now for the big question. How much light do I need? Technology has advanced so much in the last 15 years that we are constantly refining the process and updating what we know works best for growing. Current theory holds that the minimum amount of lighting needed to sustain growth is around 2000 lumens per square foot. Mid range is around 5000 lumens per square foot. Optimal is 7000-7500, or higher, lumens per square foot.

Click to expand...

what about the law of diminshing returns, Intensity = light output / by distance squared

for example my setup...
600 watt hps = 90000 initial lumens
90,000/4 =22.500 lumens at 2' from the lamp
90,000/9 =10,000 lumens at 3' from the lamp

None of my budsites are further than 3' from the lamp...most are closer to 2' from the bulb. So I guess we will see what 10,000 lumens can really do!!!