Lux Readings

[Morri]

Hi I have managed to get my mitts on a light meter and was wondering what sort of Lux should I be looking for to compare with metal halides at 18" would like to see how the LEDs compare to MH.

 

[rabbut]

Depends on the halide set-up you compare to... What wattage, brand, reflectors e.t.c...

 

[Morri]

Seem to be getting 2k Lumex at 18" as opposed to 500 Lumex at 24" in the TL550 under PCs

 

[SkiFletch]

Well, I'm not a fan of lux meters in general since they don't really tell you anything about photosynthesis. BUT, if you have one, we can make use of it.

A typical PAR reading at 18" would be around 50par with pc lamps and more like 125par with a 150 watt halide. So using ratios, 50par/2000lux = 125par/Xlux. Solve for X = 5000lux. That assumes that PAR relates linearly to lux, which is probably a safe enough assumption along the range we're talking about.

Then again, with LED's, they might have a much lower lux/par ratio since their color band is so narrow. Tough conundrum here.

 

[Morri]

Heh Thanks ski thats basicaly where I am all I can conclude is they are brighter than PC so my next step is to try a few SPS and see how well they do

 

[SkiFletch]

What wattage LED lamps are you using? And what's the spacing in between them?

As a general rule of thumb, 3-5watt LED's spaced 2" apart will behave similarly to a 150 or 250watt halide up to 12" of depth from a PAR standpoint. Beyond that depth, you'll require reflectors to maintain the halide performance as light scatter really starts to get to you.

 

[Morri]

3w at 2 inch seperation is what I went for so should be good then

 

[SkiFletch]

Yup, probably somewhere in the middle of 150-250watt halide.