400 watt HID - distance for phals & minicatts

[SheilaJ]

OK, the plant collection is growing, gotta fire up the HID light again. Problem is, I've misplaced my light meter.

Can someone give me a general rule of thumb for the distance to start them at and work them up to, so I don't burn them? I used to know all this stuff, but can't remember squat anymore, it seems!

I'm growing an assortment of phals (mostly noids), minicatts, and phaius.

The light is a 400 watt metal halide AgroSun gold, with a Radiant reflector from Hydrofarm. There's also some ambient light in the room from a bright but small west window and some fluorescent tubes.

Thanks so much!

Sheila

[Ocelaris]

I can tell you theoretically (under ideal conditions)... assuming it's about 36,000 lumens initially you come up with these numbers:

Feet away and foot candles

0.5----45,838
1----11,459
1.5----5,093
2----2,865
2.5----1,834
3----1,273
3.5----935
4----716

So, somewhere between 3-4 feet? If you want to cover more plants, then 4 feet is probably fine for lower light plants, but 3 feet is probably better if you aren't trying to cover as much area. 4 feet would probably be safe, and then down to 3 or as close as you can cover all of the plants I guess, 2 feet would be on the high end of it, more than enough for high light lovers.