400w HPS is it too close?

This is my 400w hps about 9.5" from the tops of my plants. I'm not sure if it's too close (or far away). I raised it cause I thought I saw burns on the bud leaves of my plants but i'm not sure if they were deficiencies instead, or the natural part of the flowering process. What do you guys think?

The perfect test is the hand test. You should be able to indefinitely hold your hand under the light at the same distance it is from the plant.

I had my 400w way closer than that and I don't have a cooltube, just a fan blowing across the canopy

madmad said:

I had my 400w way closer than that and I don't have a cooltube, just a fan blowing across the canopy

Click to expand...

Really? no air-cooling on the light at all? was the setup in a big room or a small enclosed area like a tent ?

i know about the hand test, i never bought that as an accurate way of measuring things. i've still burned the tops of plants in the past despite my hand feeling comfortable under the light.


my space is pretty small 3'x3'x6' with a powerful 6" inline fan connected to the cooltube but its on half speed so my tent doesnt cave in (using passive-air intake).

height looks great to me, i have never heard of the hand test before! will keep that in my mind for sure.

E.

be careful with the hand test i have had burns on my girls and the light was never uncomfortable on my hand

cyrax42o said:

Really? no air-cooling on the light at all? was the setup in a big room or a small enclosed area like a tent ?

i know about the hand test, i never bought that as an accurate way of measuring things. i've still burned the tops of plants in the past despite my hand feeling comfortable under the light.


my space is pretty small 3'x3'x6' with a powerful 6" inline fan connected to the cooltube but its on half speed so my tent doesnt cave in (using passive-air intake).

Click to expand...

Yeah really Well, my fan(its pretty big) was blowing across the canopy AND also the bulb, as the bulb was fairly close to plants( I don't think I ever had it higher than 10 inches above the canopy) and the only time I burned the tops is when I lifted the plants and the main cola touched the bulb, I didn't even realize when I did it and thought those marks are signs of some disease lol Anyway, my space is even smaller than yours - 3x2x6 and as I said I don't have the cooltube. Do you have any fan moving the air around in the tent? Also, If you take a better photo - closer to the leaves and preferrably just before you switch the light on( to keep the natural colour in the photo, without the reddish HPS hue) the wise heads here my be able to help you more, as those "burns" might as well, like you said, be deficiencies of some sort.

A 400w air cooled hood should be fine even at 8 inches with proper ventilation.