Lesson 3: Which Light?

Discuss Volker’s Light lecture here.

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where are these lectures? i dont find them anywhere.


You can click on which course you want to join here.


i tried it. it took me to GN registration.


@MK3_Pharms did you click on the individual courses on that page?

Here are the direct links for the growing at home and commercial cultivation courses.

Since you are already a GN member, you can simply enroll by clicking the button in top right [Take This Course] of each individual course page linked above.


Hey there @vritzka, et al. I just watched the lighting video, nice work. There’s a picture in there when you talk about CMH. It’s of a single ended bulb in a hood… I love the CMH lights, and I started using them when Philips made their badass MasterColor Retro-White. I used the super nice 400 Watt bulbs… and now I can’t find them anymore.
My question is this: is there a nice CMH bulb I can use on a ED18 base or socket? I’m pretty sure they all need pulse start, and so digi ballasts wont work, which is fine with me, just curious if I can use them. Also, is the industry going to make single ended bulb obsolete? are they getting phased out?
Thank you.



good questions, but honestly, I am not sure.

This is something for the tech staff at Growershouse to answer … I’m outta my depth. (Hey at least I admit it). → Growershouse contact page

I do know that the bulbs are constantly being improved. So the 400W Philips bulb would likely have a successor with improved performance.

Its impressive what the good manufacturers do to improve their lamps.

This video at 1:40 shows the testing of Gavita lamps. They have a Utrecht sphere and some other $350k equipment to precisely measure light output.


Gavita is owned by Monsanto is it not? This is personal to me but DO NOT SUPPORT them. They recently seen how much money they can make of the cannabis industry and they are definitely not in it to advance the future of this community.
Support companies that were born from the cannabis community like the fellow creators of Horticulture Lighting Group (HLG). They still visit the forum where they were birthed and answer all our questions.
Another good lighting company is Chilled Led, and Rapid LED for the DIY people.
The future is LED. I would not recommend any HID or CMH technology honestly.
End rant.


We like HLG too. Growers House has a bunch.


Thats not the point. Alot of us want to boycott gavita by not buying any of their products because they sold out to Monsanto.
They never backed the cannabis community freedom fighters before it started becoming legal. Now they want to hop on the bandwagon because they see profit. Thats not cool man. Im very passionate about this and those guys dont deserve our support at all.
Vote with your dollars!


I like my Chilled v2.

But as of now Chilled has completely stopped selling. I guess they are building something new.


Scott’s miracle grow is actually who bought gavita, but ultimately the money goes back to the monsanto/bayer mothership. And the situation is much deeper than just not supporting early cannabis cultivation. They’re buying up everyone that will entertain it. Botanicare, general hydroponics, can filters, and more.

Look into the Bayer and Monsanto business practices and how they treat farmers and agriculture in general.


The press release on the acquisition:

In case anyone is wondering what companies were part of this one acquisition:

Hawthorne, which had 2017 sales of approximately $290 million, owns leading hydroponic brands such as Gavita, Botanicare, Can-Filters, and General Hydroponics. Sunlight Supply is the largest distributor of hydroponic products in the United States. Within the last year, Sunlight opened a state-of-the-art 350,000-square foot distribution center in Vancouver, Washington and has eight other distribution facilities across North America.

Among the many benefits of the transaction, Hawthorne will possess the most technologically advanced supply chain in the hydroponic supply industry. By being able to ship directly, Hawthorne will have greatly enhanced relationships with hydroponic retailers, giving it greater visibility into current market trends, retail inventory levels and point-of-sale data that will allow it to operate more effectively.

Once we see federal-level legalization I’m sure we’ll see big tobacco and big pharma buying into and consolidating the consumer side as well. Do U.S. monopoly laws still have teeth to them?


These aquisitions look scary, for sure.,

But this seems to happen in most markets, so its no use fretting over it.

If you are a producer, put a brandname on your produce. You can then build your own customers.

If you don’t brand your produce, you could end up like the milk farmers who can’t make a profit on their milk.


Absolutely spot on! Produce the best product, then build a brand that consumers ask for by name. Cannabis producers are uniquely placed to reap great benefits from brand marketing, as there are many exciting stories to tell.


That’s about how I see it. No fretting here, just not buying or supporting any of their products.


I’m doing my best not to support them either, but who knew Hurricane fans? Well, now I do.


A lot of commercial-scale growers in LA were confused by the success of Gavita as primary lighting which reduced the footprint from 5’ x 5’ (Magnum XXL hoods) to 4’ x 6’ and were designed as supplemental lighting. It was finally chalked up to marketing and lack of experience as it had the effect of lowering yield for many layouts until the DE bulbs hit.

Also, it makes no sense to have the heat-generating ballasts in the bloom room. Still, everybody bought into it.

In commercial ag they ran the #GlyphosateIsVital social media campaign using unions to do the dirty work for them. Bayer just got hit with their 3rd judgement for Glyphosate related cancer with $2 Billion USD awarded.

At any rate, their business practices are definitely coming under fire with criminal indictments in the works. Perhaps as a result, one day the drive for profit at any social cost will work its way out of the system.


@JoeGrow, I’m steering clear of the politics but to the 4’ x 6’ spec: check out the intensity map of a Gavita 1K DE.

These things were originally designed for supplemental lighting in greenhouses and not to be checker boarded in warehouses. This is a 5x5 area at and I think 1M mounting height. Uniformity only happens at 36 inches or better from canopy.

Even the “bar” LED fixtures have a hotspot if not ganged together for overlapping light:


Yep, looks like 4 x 6 to me (24 sq ft) vs 5 x 5 (25 sq ft) for Magnum XXL (SE)