I know that i can stick a magnifying glass under my 400w hps(trying to solar puff indoors) and nothing happening cant start a fire. I go outside and not only can i not look at the bowl but it lights instantly. I can feel the sun on my arms much more than my hps, i really dont see how you can compare the 2
You are mistaking radiant heat with lux. Here is an example. If the tempature in your grow room is 70 degrees, why will the plant burn if it is too close to the light?
(Major Toke)
" Essentially there are two aspects to the thermal environment that you need to be aware of:
1. The AIR temperature
2. The
RADIANT temperature
Although obviously related, these are 2 distinctly separate phenomena and your plants have different tolerances for each.
1. Air temperature
Your standard mercury/alcohol-bulb or digital thermometer is designed to measure the temperature of the air (But not
radiant heat). This is what is being referred to in the usual growers 'rules of thumb' such as maintaining your grow above 16degC and below 30degC.
Most thermometers are only designed to measure air temperature growers often mistakenly place their thermometer in direct light;
radiant energy will warm your thermometer and give a higher than actual reading.
2. Radiant temperature
Radiant temperature is the result of heat transfer bewteen objects at different temperatures without whats inbetween i.e. the air, being effected. In our case the plants are naturally at a lower temperature that the light and reflector so heat is transferred to the plants foliage from the light/refecltor through radiation. This causes the leaves to heat up. The plants can withstand much higher
radiant temperatures (around 40-50degC) than they can air temperatures but if this is too high the plants can 'burn'.
The plants can withstand much higher
radiant temperatures than they can air temperatures, but if this is too high the plants can burn.
'The hand test': Place your hand in a comfortable position for some time at the tips of your plants should be. If your hand feels hot, then the lights are too close, the
radiant energy is too intense, and light burn may result. Do this test and raise your HID lights/reflectors periodically to keep light burn to a minimum. "
Another way to see the diffrence is to put a thermometer in a bottle of water and hang it at the top of the plant canopy. You will see it warms up hotter than the room tempature.
You could also compare a CFL to an incedescent light bulb. A CFL puts out more light, but the incadecent puts out more heat and yet it is dimmer.
If your sister has an easy bake oven look at the heat source, its a 100w light bulb, thats right enough to bake a cupcake but a 23w cfl puts out the same or more lumens (in the right spectrum) using 1/4 the power with no heat.