Can a plant get to much light?

I have a 80cm x 80cm x 1.2m or 2.8ft x 2.8ft x 4ft cupboard with a 400w globe. MH for veg and HPS for flowering. 300 square feet per minute extraction fan??

yes a plant can get too much light (the leaves will bleach) But you don't have to worry about that, if you have your light too close you will burn the tops with heat before you will bleach them with a 400w.

I'm in for the ride. I really don't see that light working in that space without a cooltube and some serious cooling mods. On the burn/bleaching front your kinda guaranteed the plants are gonna be in a bad bind. With the 400w you're losing 2' in the gate with the height of your light fixture, mounting hardware and the 1' or so distance between your ladies and the bulb. This is mitigated with the cooltube and you will be able to get closer. So with the 400w and no tube figure you got a 2.8' x 2.8' x 2'ish. A 250w would fit that space better but it may not be an option if you already own the 400w.

Yep what Spanky said! Also you don't mention if you have an intake fan, your gonna need some very good airflow in a small space using hid lighting, and almost certainly a cooltube.

I dont have an intake fan but did drill holes in the bottom of the cupboard for air intake. Extraction fan is installed right opposite globe on top.

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I've bleached my centre plant.
Swapped from 600w to 1000w and the growth directly beneath the ventilated hood quickly went from lush, moist, dark green
to dry, papery looking, lime green.
The trim leaves have lots of purple - but it looks different to 'natural' purple.
Almost like scar tissue....if that makes sense???

I've uploaded pics in another thread about bleaching.

You're gonna need to cooltube that light. You're 300cfm fan may be able to keep temps reasonable with proper light clearance. However, your ladies won't be able to breath in the wind tunnel created by pulling all that air through that small space quickly. An intake fan wont be useful until you're trying to pull out more air then your intake solution can draw in. Have you tried running this setup for a few hours/days without plants? You want everything in the grow space running including your circulation fan(s) to get an accurate idea of the temp/humdity environment.

only time i ever got light bleach was when i used 1000w HPS in a 3x3x6 area, so i dont think you need to worry about getting too strong light intensity.
However like other have said it will be hard for you to use 400 w in such a small space (especially since its so low..) without a cooled hood or cooltube.
You really should invist in this, as should all people who grow with Hid lights in smaller spaces. why? because the lightloss you get from i.e a cooltube is nothing compared to how much closer to the tops you can get and how much easier the grow area will be to control.

a good rule of thumb is 50w hps/sq. ft.. I myself like aiming for 30-50 watts per square foot for veg. 50-75 watt per square foot for flower. I got the best results doing this.

Make sure you take into account the distance from light to tops when you calculate this since light intensity dimishes fast the further away the light is placed from the tops. here you can see how light intesity decreases depending on distance from tops
HPS ChartView attachment 2994579
MH Chart View attachment 2994580

Remember, bulbs from different producers have slightly different outputs so remember to check on the model you have when making calculations.

Be VERY carful with high temps because they will cost you a lot of yield and make your buds a lot more airy than they should be. Many make this misstake, actually i would say its the no.1 reason for dimished yields.

Honestly you should think about making your growarea a bit taller if possible. around 160-180 cm. This would increase your ability to control the temperature inside your growing room.

best regards!

Thanks for all the info. It explains alot on my first test run (example attached). Unknown strain, grown from seed, fed Nitrosol 80g/kg N, 20g/kg P, 58g/kg K. Before I switched to flower (1-01-2014) I noticed leaves far tips yellowing and curling up so I changed to only clean water. I didnt prune so got lots of pop corn but buds starts to swell now. See attached pic's

What's the temps in that grow space?

Average temperature is in hot afternoon is 27°c/80°f. And average trough night is 20°c/68°f

Good shit. Next grow you may want to try LST or Scrog to keep her off the light and you'll be getting some big buds. My best advice is to find a bigger grow space for that light. 400w is good for a bigger room with more plants. You're current setup is wasting a lot of energy to grow 1 or 2 medium size trained plants.

Nice lookin plant man~

Thanks man, this is how it looks a week later.

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I seem some burn marks on her, but if you're saying the temps are good, then the temps are good.
But think about the temps right next to that top cola, that's a couple inches from the bulb, it's godda be in the 90's...

View attachment 3019593View attachment 3019594

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Thanks for the info. Now I need to ask if you think its ready?

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