Futuregrower

Ever have one of those moments? Where you say, Oh THAT'S what they mean?

Just figured out - if I build a grow cab 2 X 4 X 7 feet, its 8 square feet, right? (1) 600 Watt HPS bulb, is about 90,000 lumens. Roughly good figure industry wide. The grow guide says about 25,000 - 50,000 lux is optimum.

Lux is lumens per square meter. So, my cab is 2 X 4 feet, or about .74 square meters.

So, 90,000 lumens over the .74 M2 area is 66,600 Lux. for my cab.

Assuming I can keep the temps cool I'm using this. HOWEVER, I've seen info on here that over 50,000 lux is too bright.

But using the rule-of - thumb method of Watts/Sq ft, I have 75, which is right on between 50 minimum and 100 max.


What do you think? too many LUX?
( I'm not even going to get into PAR Watts, one step at a time)

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The futures here, we are it, we are on our own....Singing Ashes, ashes all fall down......

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buzzmobile

Seems about right to me. Cooling the grow space may be a challenge.

Here's a lighting thread to check out.

mayan

Good lux with your grow!

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Futuregrower

Thanks Buzz and Mayan, I'm planning on having a DIY cooltube that draws air in from outside, and I've got Dimmable Ballasts, so if it's too hot I can go to 500 or 400 Watts. Love those dimmable ballasts! My 600W will start a 400W bulb, if the switch is set to 400 Watts.

Also, I'm setting it up, then letting it run for a few hours before I ever put anything in it, just to check temps.

Mainly what worried me is the LUX- over 50,000 is a lot, so I've heard.

__________________
~~ The Once And FutureGrower
The futures here, we are it, we are on our own....Singing Ashes, ashes all fall down......

"I inhaled, frequently," Senator Obama said before being elected President "That was the point."

First Grow! Twofer, Mandalas "Satori" and KC Brain's "Northern Lights Special"
http://www.gardenscure.com/420/hydro...kc-brains.html

Caution! (Do not stop on tracks). Grow 2

LINK to a great way to search, written by Burndt

knna

Yes, Futuregrower, you are on the right track.

Unfortunatelly, its more complex than that.

You can calculate the total light in the grow area and divide it by the surface area, either on sq meters or sq ft, and get the average light's density.

But light is not distributed evenly. Depending of the type of light, the hood and the distante to plants, it may be more evenly distributed or very unevenly.

A difference of 15-20% between the point of the canopy with highest lux and the lower is considered excelent, and almost impossible to get using a single point of light. Its usually only achievable using fluorescent tubes or LEDs. For HID, its not rare to find differences of 100% on the light distribution at the canopy level, meaning on the center there is double lux than in the sides.

And this only relates to the top canopy, that you can visualize as an horizontal plane. So we have been talking about horizontal distribution of the light. The toughest job is to get an evenly vertical distribution, along the height of the plants. Generally, here the differences are really huge.

You are right in the sense that what matter is the lux at leaves. But its impossible to calculate it. You need to measure it using a light meter. Any one serves for this task, as we work with so high light densities that the error margin, still of the cheapest luxmeters, is unnotiable. But you need to ensure the lightmeter have a good max. Many of them reach just to 20Klux (1Klux=1000lux) or 50Klux. Below a HID, almost always you are going to have figures way over that. A lightmeter for grow lighting measurement may reach a minimum of 100Klux, and preferably, 200Klux.

Measuring the lux in each area of the grow gives you very valuable information to improve your grow. It allows you to identify the areas with too low light that need to be suplemented and to put the light at the optimal distance over plants.

Cannabis may support 125Klux of HPS without any problem. Light bleaching often only happen past 200Klux.

In general,the higher lux on a area, the higher total production (g/sq ft), but the lower productivity (g/W).

As the btotal light on the space is given, the better you can distribute it, the highest the productivity, thus the higher production of the grow area. So measuring your grow area with a light meter is a great way to improve your grow, and a good info to put your results in perspective.

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