Loss of light on HID units due to distance caused by heat...

Since HPS and MH fixtures generate so much heat, is it safe to say that because you can place fluorescents and CFLs more than twice as close to your plants, that you are essentially needing half the lumens when comparing to an HID? If in reality all one would be getting with an HID is say, half, does that mean that a fluoro setup, given the right amount of lumens say 13,000 can be equal to a 250 watt HID if placed twice as close? Especially since fluorescents have a more favorable color temperature for plant growth? I know that there is a certain math behind all of this but I really don't know this math! Please help shed some light! :)

I can't say it technically.....but no. And I'm afraid I can't agree with you that and HID light has a poorer spectrum than a cfl. Metal halide is excellent for seedlings. Perhaps you are thinking of HPS llighting?

Your idea is good....I wish it were true but I'm afraid it isnt. There is a formula somewhere....perhaps Jorge Cervantes book. Number of lumens at one foot = X
Drop down another foot and it's X divided by four. Another foot and its X-divided by 9
Next foot down....X divided by 16.

I just read this yesterday so that's why I remember it. But I don't think if you have your cfls at 4 inches (13,000) lumens....your 250w MH...Perhaps...25,000 lumens from one foot away. I'm afraid your cfls' lose.

Hmmm, interesting. I guess I was wrong in assuming that light intensity doubles or divides by half with distance. Thank you for your help!

Well I'm still trying to figure out how to say it.

cfls....13,000 lumens is the best youll ever get from them. At one inch, at six inches, you will NEVER get more than 13,000 lumens...you see what I mean? Your cfls are also pretty useless at anything beyond...say....a foot. So they are only good for one foot of light anyway.

So an MH bulb ALREADY starts with TWICE the lumens (25,000) and its already DOUBLE the distance...(1 foot)...or perhaps even MORE than double the distance than a cfl. Still starting with 25,000 lumens. It just can't lose that race.

Drop it back to two feet from target.....5000 lumens and so on.....

I see... I am thinking of getting a 250 or 400 watt HID, they have some cheap ones new on ebay I hope getting the cheaper ones doesn't make a big difference compared to the more pricy ones. On the other hand I am very interested in those 'T5' lights, one of the recent threads turned me on to them, too bad they are very expensive. What do you think about these?

Personally....I love HID lighting. I think it's one of BEST...if not THE best investment you will make. DON"T skimp here.....I'll go with cheaper nutes before I go with lesser lights....seriously. There just isn't any replacement for actual lumens etc and your plants will know the difference and thank you for it many times over.

You will spend X time, energy etc etc on these plants as they grow. They will take however long to finish....(3-4 mos) and during that time you can double your yield JUST by using quality lighting vs "less than ideal" ....you do nothing else...assuming plants are healthy and such (pay light bill maybe...but it will be worth it) Not only will your yield be lesser if you use anything less than the best (HID) , your plants may take longer to finish according to some experts.

Amount wattwise.....a 250 watt HPS (I'm going to assume you are buying ONE light for both flower and veg....that would be HPS although metal halide HID lighting is better for vegging....we won't go there) will cover a 2 x 2 area of plants.....a 400 watt will cover a 4 x 4 area. In my opinion...good grow lighting is like computers. Buy more than you think you'll need....you 'll find something else to put use it for in no time at all. ;)

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Originally Posted by Weedhound

Personally....I love HID lighting. I think it's one of BEST...if not THE best investment you will make. DON"T skimp here.....I'll go with cheaper nutes before I go with lesser lights....seriously. There just isn't any replacement for actual lumens etc and your plants will know the difference and thank you for it many times over.

You will spend X time, energy etc etc on these plants as they grow. They will take however long to finish....(3-4 mos) and during that time you can double your yield JUST by using quality lighting vs "less than ideal" ....you do nothing else...assuming plants are healthy and such (pay light bill maybe...but it will be worth it) Not only will your yield be lesser if you use anything less than the best (HID) , your plants may take longer to finish according to some experts.

Amount wattwise.....a 250 watt HPS (I'm going to assume you are buying ONE light for both flower and veg....that would be HPS although metal halide HID lighting is better for vegging....we won't go there) will cover a 2 x 2 area of plants.....a 400 watt will cover a 4 x 4 area. In my opinion...good grow lighting is like computers. Buy more than you think you'll need....you 'll find something else to put use it for in no time at all. ;)

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some people swear by CFL's:wtf: but if you want fully developed crops use HPS or MH bulbs:greenthumb: