Lighting Question

bgold420

bgold420

Active Member
How far should my 1000watt MH be from the tops of my plants during Veg ...
as well as how far should it be when i switch to flower with the 1000watt hps ?
 
desertrat

desertrat

Well-Known Member
use your hand as a temperature gauge, placed at the top of the plants. lower your light as far as you can with your hand being comfortably warm but not hot. if you are using air-cooled hoods or cooltube you'll be able to get the light to within a foot.
 
max316420

max316420

Well-Known Member
desertrat said:
use your hand as a temperature gauge, placed at the top of the plants. lower your light as far as you can with your hand being comfortably warm but not hot. if you are using air-cooled hoods or cooltube you'll be able to get the light to within a foot.
Click to expand...
THANK YOU, this dude on another post told me that was wrong, and thats they way i have been measuring it for years and has worked great for me
 
desertrat

desertrat

Well-Known Member
max316420 said:
THANK YOU, this dude on another post told me that was wrong, and thats they way i have been measuring it for years and has worked great for me
Click to expand...
to be fair it gets a little confusing because you measure radiant heat with your hand and use a thermometer shaded from direct light to get the ambient air temperature. both are important for growing.
 
J

jdizzle22

Well-Known Member
What if you have a reflector with the glass and fans blowing on the plants? I have a 400w hps in a yield master 2 supreme and it would seem that I can get as close as 2 inches to the glass, even without a fan blowing across the tops.
Is that still too close even though my hand feels fine?
*is the hand method EVER wrong?*
 
bgold420

bgold420

Active Member
hmm ok ... yeah my hood is air cooled with a 8 inch centrifuge fan ... light stays nice and cool ... im going to lower it tonight when my cycle starts again ....

Question .... will they really grow that much better if the light is closer ?
 
desertrat

desertrat

Well-Known Member
jdizzle22 said:
What if you have a reflector with the glass and fans blowing on the plants? I have a 400w hps in a yield master 2 supreme and it would seem that I can get as close as 2 inches to the glass, even without a fan blowing across the tops.
Is that still too close even though my hand feels fine?
*is the hand method EVER wrong?*
Click to expand...
the hand method is perfect for measuring radiant heat, but with a strong light close up you have to worry about too much light as well as heat. by bringing the light that close you are providing far more light than the sun which can hurt your plant.

bgold420 said:
will they really grow that much better if the light is closer ?
Click to expand...
as long as you're not exceeding 10,000 lumens per square foot they will grow better the closer the light.
 
max316420

max316420

Well-Known Member
honestly i have never seen a marijuana plant get TOO much light, as long as they are not to hot or burning them you'll be all good
 
Bonzi Lighthouse

Bonzi Lighthouse

Well-Known Member
desertrat said:
to be fair it gets a little confusing because you measure radiant heat with your hand and use a thermometer shaded from direct light to get the ambient air temperature. both are important for growing.
Click to expand...
Yeah he conveniently left that part out. I've had to learn about dealing with heat in enclosed spaces the hard way. BTUs, WATTs, AMPs, CFMs and Ambiant Temps. Variables and Constants, control the variables and understand the constants = big bud.
 
Bonzi Lighthouse

Bonzi Lighthouse

Well-Known Member
jdizzle22 said:
What if you have a reflector with the glass and fans blowing on the plants? I have a 400w hps in a yield master 2 supreme and it would seem that I can get as close as 2 inches to the glass, even without a fan blowing across the tops.
Is that still too close even though my hand feels fine?
*is the hand method EVER wrong?*
Click to expand...
Yes, and in the post I answered the rule of thumb was not working for him. The fact that it works for you is great for you, but there are many far more important variables to consider.
 
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