Metal halide vs full spectrum LED for veg

[Piper.180]

Hi all I've been wondering if I should go back to using metal halide for veg. Ever since switching to LED I've noticed my internode length is a longer. This makes sense as my LEDs colour spectrum is lower end of 3000k and my MH bulbs were 6000k.

I'm wondering if switching back to MH would be worth it as they are less efficient but I miss the tight nodes and stacked colas. 

I was planning to use MH from mid veg to week 3 flower to create a more desirable plant structure and then switch back to LEDs for the rest of flower. I was hoping this would create more bud sites and lead to bigger yields due to colas being stacked making better use of the vertical space. 

 

 

Edited April 7, 2023 by Piper.180

[KC]

Just out of interest, what Mh bulb were you using? I don't think I ever saw a 6k. Mine were 4200k I think. 

[Piper.180]

28 minutes ago, Fatboy77 said:

What led are you using in veg, what setting and how far is it from the plants?

I use a Telso 8 in one tent for veg and then turn the second one on for flower, hanging height is 60cm.

 

In my other tent I have a HLG 600 rspec running at around 60% for veg and at 60cm hanging height. 

 

I've played around with hanging height and the dimmer on the HLG and the plants can't handle anymore intensity, they just start drooping and going yellow on the tops, I also lose a lot of light spread going any closer and don't see any improvement with internodal length. Both lights are at the lower end of 3000k so lots of red, most LEDs are like this as LEDs are inefficient with blue wavelength so they put extra red to get the efficiency up. 

Edited April 7, 2023 by Piper.180

[Piper.180]

Just now, KC said:

Just out of interest, what Mh bulb were you using? I don't think I ever saw a 6k. Mine were 4200k I think. 

I can't actually remember, it just remember it was in the 6000k range. I thought I had it stored away but I can't find it anywhere. Sunmaster Cool Deluxe Metal Halide Bulbs are 7200k, which was the bulb I was looking at to replace my old one I can't find

[catweazle1]

multiply by 0.017. 20-30 quid.

Edited April 7, 2023 by catweazle1

[Herbal Kint]

10 minutes ago, Piper.180 said:

I can't actually remember, it just remember it was in the 6000k range. I thought I had it stored away but I can't find it anywhere. Sunmaster Cool Deluxe Metal Halide Bulbs are 7200k, which was the bulb I was looking at to replace my old one I can't find

It's a great bulb,I used it for veg and flower as well,has kinda weird shape.Runs hot ,much more then led so take that into account as hot weather is coming

 

I'd imagine same wattage led would be more effective tho

Edited April 7, 2023 by Herbal Kint

[Piper.180]

Just now, Fatboy77 said:

What temperature do you aim for in veg

I aim for 77 lights on and around 71 for lights off. 

Definitely tighter than what I'm getting at the moment with my LEDs. Maybe it's just the pheno. What LEDs are you using? 

[Piper.180]

Just now, catweazle1 said:

multiply by 0.017. 20-30 quid.

I use a PPFD meter on my smart phone, you can calibrate it to existing PPFD grid maps from light manufacturers and it gives pretty accurate results. 

[Piper.180]

Just now, Herbal Kint said:

It's a great bulb,I used it for veg and flower as well,has kinda weird shape.Runs hot ,much more then led so take that into account as hot weather is coming

 

I'd imagine same wattage led would be more effective tho

They are definitely more effective, it's just the colour temp where I think LEDs fall short. HLG have started making 4000k LEDs now to try and get more blue in the spectrum but they're almost £900 and I need 2 of them and they're really only for veg. That's a lot of money for me. 

[catweazle1]

Just now, Fatboy77 said:

You may as well be speaking Afrikaans.  Those are monopoly numbers to me.  I've found heat can cause stretch.

I use a variety of led's, but those are under maxibright 660's with additional strips.  I don't see much difference between any of my led's tbf.

I use bar led's, boards direct heat down towards the canopy more.

I was thinking a high night-day heat difference doesn't help stretch.

[KC]

Hlg have always had a large amount of blue in. I don't veg under mine though so can't say how it fares. 

[catweazle1]

I have 3 different leds and currently using a 315w cmh for its heat. I'm not sensing any growth difference between them, other than I use less watts with led.

[Piper.180]

8 minutes ago, Fatboy77 said:

100%.  I have a really defined method for controlling it, works a treat.

Are you using negative diff? If so, how are you achieving it? 

 

Also, nice light. I wanted that as well but my tents are too small. 

[Military Grade]

Newer boards have the diodes concentrated at the corners for better spread, something to consider when buying a new LED board.

[Piper.180]

41 minutes ago, Fatboy77 said:

Don't go over 27c for lights on temps for the 3 weeks of stretch.

First two hours of lights on are really important, so you either need to be on hand or automated lights.

I use a soft start. 

I open the tent at lights on to water, at this point I turn my led down 50%. 

If there's any heating on I turn it off for the first 2 hours.

Opening the tent and dropping power means the first hour of lights on there won't be a temp increase, maybe even a slight drop.

After watering I turn the light up 25%.

After two hours I turn the light up to full and if heating is being used, turn it back on.  But stay under 27c.

I'll give this a try, I never thought about opening the tent to be honest. The Telso doesn't come with a dimmer so hopefully just raising it up to the extraction system will help with the heat from that. Thanks for the help.