How do you measure light????

M

mosess187

Member

• Oct 9, 2005

• #1

I've been searching every where and no one seems to know how to measure light wattage per plant(s) in a grow area.....using the specs. of your cab grow....does anyone have any info on this subject matter?

 

Dutchgrown

----

Veteran

• Oct 9, 2005

• #2

Well, not sure if this is any help in arriving at the light intensity emitted per square foot
based on different wattages of lights and distance of the specific light from the plant(s).

dg

 

mean mr.mustard

I Pass Satellites

Veteran

• Oct 9, 2005

• #3

Light meters can be found. If I were you I would project how many plants (or fractions of plants) would be in a sq ft of your cab space to find out how that relates to the typical unit of referral (watts per square foot). Typically growers drop their bulbs as low as allowed by heat buildup to achieve the most intense light. Therefore it is basically variable only by the wattage of the lamp(s). Also like DG said before, there are different types of light from different bulbs that may be taken into account.

 

Rodriguez

Member

• Oct 10, 2005

• #4

just watched a really good documentary about light, wish i could remember it

 

NiteTiger

Tiger, Tiger, burning bright...

Veteran

• Oct 10, 2005

• #5

The technical name is a photometer, I believe, and can be found in high-end camera and photography stores.

I could be wrong though, it happened once before, back in '88...

 

GMT

The Tri Guy

Veteran

• Oct 10, 2005

• #6

With a really long tape measure.
No seriously, its lamp watts divided by square feet of the floor space. So a 2x4' to acheive 50w per sq' will need a 400. 2x4=8 400/8=50

 

G

Guest

• Oct 10, 2005

• #7

I use an old camera with a light meter inside. Lay the cameras flat on the surface to be measured and you get the answer.

Light works, normal to and parallel to surfaces at different rates of exposure.

Avid

 

Rodriguez

Member

• Oct 11, 2005

• #8

That graph is pretty cool thanks DG

 

M

mosess187

Member

• Oct 11, 2005

• #9

Thanks dearly to everyone on the info......I've been dying to get this second grow off the ground....hopefully i can put something together to get the most out of my plants.....i'm still learning though so wish me luck!!

 

sunnyside

Plant Manager

Veteran

• Oct 11, 2005

• #10

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.

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.

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

To measure light in terms of wattage is flawed. We should refer to lumens for a better reference. Example is a 1000 watt MH vs a HPS the HPS has the same wattage but 1/3 more lumens.

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...

hope this helps...

 

Verite

My little pony.. my little pony

Veteran

• Oct 12, 2005

• #11

Even the lumen scale has been replaced by PAR, photosynthetically active radiation, for the standard of light to plant response. It also takes into account the spectrum of light the bulb gives off in its measurement.

 

G

Guest

• Oct 12, 2005

• #12

I just use a cheap sun tanning meter...figur if it says I need to turn over withen 30-45 minutes = enough light in that area for my plants