Light height and spectrum question

sunny747

sunny747

Well-Known Member
I saw a video where a guy was saying that even though temps may be fine it is undesirable to keep lights close to canopy. He says the plants won't get the correct spectrum and the fan leaves will stay small.

I run 400w hps in an air cooled hood in a 3x3 tent. I keep the light maybe 14-16 inches above the canopy. Just high enough so that I get even coverage.. Should I raise my light or is it fine where it's at?
 
I want to say that the distance in which your lights are to your plants have nothing to do with the spectrum of light. That spectrum comes down to your bulb.

Also I'd lose the air cooled hood and find a different way to cool it down. Open reflectors are better the glass diminishes the light your plants recieve a bit
 
pseudobotanist said:
I want to say that the distance in which your lights are to your plants have nothing to do with the spectrum of light. That spectrum comes down to your bulb.

Also I'd lose the air cooled hood and find a different way to cool it down. Open reflectors are better the glass diminishes the light your plants recieve a bit
Click to expand...

Yea, I think this winter i will try taking out the glass... Thx'
 
pseudobotanist said:
I want to say that the distance in which your lights are to your plants have nothing to do with the spectrum of light. That spectrum comes down to your bulb.

Also I'd lose the air cooled hood and find a different way to cool it down. Open reflectors are better the glass diminishes the light your plants recieve a bit
Click to expand...

What he's loosing is certain spectral ranges....The UV ranges......Borosilicate glass is used in bulbs, windows and any application where sun or high intensity lighting is made and used for just that reason. Reduction in harmful to human UV bandwidth light..

You'll not gain a significant enough amount of light photons to warrant not using your hood....

Doc
 
I al
Dr. Who said:
What he's loosing is certain spectral ranges....The UV ranges......Borosilicate glass is used in bulbs, windows and any application where sun or high intensity lighting is made and used for just that reason. Reduction in harmful to human UV bandwidth light..

You'll not gain a significant enough amount of light photons to warrant not using your hood....

Doc
Click to expand...
I also have a hood with glass, I was going to take the glass off this winter. Opinion?
 
Dr. Who said:
What he's loosing is certain spectral ranges....The UV ranges......Borosilicate glass is used in bulbs, windows and any application where sun or high intensity lighting is made and used for just that reason. Reduction in harmful to human UV bandwidth light..

You'll not gain a significant enough amount of light photons to warrant not using your hood....

Doc
Click to expand...


The glass in the hood isn't made from borosilicate. It actually blocks 15% of spectral output.

Uv can only pass through borosilicate glass. Any other glass , when uv hits the glass it converts to IR. Most hps se bulbs don't put out uv anyway.

Small amounts of uva and uvb is very beneficial to plant growth.
 
Dr. Who said:
What he's loosing is certain spectral ranges....The UV ranges......Borosilicate glass is used in bulbs, windows and any application where sun or high intensity lighting is made and used for just that reason. Reduction in harmful to human UV bandwidth light..

You'll not gain a significant enough amount of light photons to warrant not using your hood....

Doc
Click to expand...

Thanks doc. Looks like I gotta read up a bit more. Here's a pretty cool link I came across if anyone is interested.

http://www.controlledenvironments.org/Growth_Chamber_Handbook/Plant_Growth_Chamber_Handbook.htm
 
Dr. Who said:
Why? Heat? It supplies plenty of radiant heat! Try with it in first and take it out if you have to...
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It gets very cold in the winter so I obviously use that to my advantage, I didnt realize the glass diminishes necessary spectrumsnor whatnot as hyroot said.


Will have to do some reading on the subject. Thanks guys.
 
hyroot said:
The glass in the hood isn't made from borosilicate. It actually blocks 15% of spectral output.

Uv can only pass through borosilicate glass. Any other glass , when uv hits the glass it converts to IR. Most hps se bulbs don't put out uv anyway.

Small amounts of uva and uvb is very beneficial to plant growth.
Click to expand...

A quick call to a manufacturer and speaking with a design engineer, he said....."unless your buying real cheap hoods from China. Borosilicate glass IS used by us and most makers of lighting products for the horticulture industry for 2 reasons......It does NOT restrict light passing through it (except for the UV range) and it's thermal properties in relation to strength and the liability of possible injury."

When asked about Bulb glass, he said " MH and far more so for Mercury Vapor the outer glass is Borosilicate TO reduce harmful UV emissions....This is actually a Government requirement for MV and some MH......I've been told that the newer low spectral bulbs from EYE have overcome heat and arc problems and don't use it for more low nm ranging."

I just had to confirm this as I was told this by another bulb maker some years back and I had to be sure I had it right....

He DID say I was wrong about window glass - That's Soda-Lime-Glass and it stops some minor light pass through...

Root, not trying to argue Ok?

Doc
 
Dr. Who said:
A quick call to a manufacturer and speaking with a design engineer, he said....."unless your buying real cheap hoods from China. Borosilicate glass IS used by us and most makers of lighting products for the horticulture industry for 2 reasons......It does NOT restrict light passing through it (except for the UV range) and it's thermal properties in relation to strength and the liability of possible injury."

When asked about Bulb glass, he said " MH and far more so for Mercury Vapor the outer glass is Borosilicate TO reduce harmful UV emissions....This is actually a Government requirement for MV and some MH......I've been told that the newer low spectral bulbs from EYE have overcome heat and arc problems and don't use it for more low nm ranging."

I just had to confirm this as I was told this by another bulb maker some years back and I had to be sure I had it right....

He DID say I was wrong about window glass - That's Soda-Lime-Glass and it stops some minor light pass through...

Root, not trying to argue Ok?

Doc
Click to expand...


I wasn't referring to the bulb glass. I was talking about the sheet of window glass in an air cooled hood.

My induction lamps use borosilicate glass as well. They put out about 5% uv-a and 3 % uv-b. My old cmh's put out more uva and uvb and very small amounts of uvc. My cmh's also have a quartz crystal coating.
 
hyroot said:
I wasn't referring to the bulb glass. I was talking about the sheet of window glass in an air cooled hood.

My induction lamps use borosilicate glass as well. They put out about 5% uv-a and 3 % uv-b. My old cmh's put out more uva and uvb and very small amounts of uvc. My cmh's also have a quartz crystal coating.
Click to expand...

That's what I called about.....That IS Boro in the "good" hoods......The bulb glass was the second question ...

lol

Doc
 
'Light Distance' is relative to area covered, as you move the light futher away you can fit more plants under it but they each get less light.

The inverse square law of light says that at one foot from the bulb half the light is lost but that light now covers twice the area.

You can jam your plants as close to the light as possible but youll only fit one or two under it, distance is relative to how big you want your plant canopy to be and quite often it is a bigger light you want rather than trying to get as close as possible.

:-)
 
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