watts or lumens?

[mojo]

when deciding ho much light is required for a given area, should I be considering watts per sq.ft., or lumens per sq. ft.? What about colour temp.(2100k)? Calculating lumens by sq. ft. doesn't seem accurate, without taking the distance from lamp into account.
Is there a way to estimate lumen reflection (ie;off styrofoam)? :eek: :confused:

[green girl]

As a basic rule or thumb I like to use these figures:

30 watts or 3000 lumens per sq ft for vegging minimum.

50 watts or 5000 lumens per sq ft for flowering minimum.

[Pistol Pete]

Heres A Great Links For Y'allhttp://www.growingedgetechnologies.ca/content/lots_of_information/D_Light_square_footage.pdf

Its Thorough!!
PP

[salmayo]

Human Red chromens = Lumens * red coordinate/green coordinate.

Chromaticity coordinate standards (given for a theoretical Human eye)
x = red index
y = green index
z = blue index

most similar lamps with the same color temperature have fairly standard index values for things like HPS/MH.

This data is available from the engineering bulletin data available on most lamps.

This helps out a lot if you are trying to quickly compare sources for Blue and/or Red.

Plants don't care much about green light, so lumens alone aren't worth much, but they can be used to calculate more precise Red and Blue numbers.

[Richard Owl Mirror]

As a basic rule or thumb I like to use these figures:

30 watts or 3000 lumens per sq ft for vegging minimum.

50 watts or 5000 lumens per sq ft for flowering minimum.

Hello Green Girl, could answer questions posed in a post I wrote.

OwlMirror's Medical Marihuana Perpetual Garden by Richard Owl Mirror
You can find it under Advanced Techniques & Experiments on this forum.

The question centers around if two 150 watt HPS would be sufficient to illuminate a growing environment that equals approximately an area constantly @ 36" long, 24" deep and, a mere 24" in Height.
It would be used to grow and harvest a revolving series of 8 auto-flowering plants which do not grow more than 12" high on average.

If the strength (THC %) is enough to resolve a medical marihuana patients needs and a solution can be found to replenish the seed stock. I believe a low-income, qualifying patient could supply themselves in perpetuity with minimal costs.

Could you help me understand if I'm on a valid track by leaving a comment on my article ?