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mikethecactusguy wrote: ↑Sun May 16, 2021 3:48 pm 10,000 lumens at plant surface is the minimum you want to grow plants indoors. Forget about watts and amps and everything else. 12,000 lumens is shaded sun intensity. What does this mean. You have to physically measure the light that reaches your plants. If a Lamp outputs 5000 lumens that is its rating at the lamp surface. It will drop substantially 12 inches away at the plant surface. Download a light meter app for your phone and use it. Buy enough lights to get 10,000 lumens at plant surface. That is the easiest what to explain lighting.

Okay, thank you, that makes more sense.

Unfortunately, I actually don't have a mobile phone, but I could buy a lux meter; I've been indecisive about which brand to buy (my budget is under $50), and the negative reviews seem to be coming from experienced growers/photographers; as opposed to a majority of positive reviews mainly from less-experienced individuals, it seems. I've considered getting one for about a month, but I haven't made any decisions yet.

Hopefully my current light will, at best, help transition my plants to full sun outdoors; I'm really not sure, as I have no way of proving/analyzing the light's spectrum, PAR/PPFD values, etc. I just have to rely on the manufacturer's claims.

Why does it have to be a big deal? All you need is a meter that will give you a reading that is close. You're not doing anything that requires a high degree of accuracy. Just buy a cheap meter and work at getting the light correct for the plants.

mikethecactusguy wrote: ↑Sun May 16, 2021 11:59 pm Why does it have to be a big deal? All you need is a meter that will give you a reading that is close. You're not doing anything that requires a high degree of accuracy. Just buy a cheap meter and work at getting the light correct for the plants.

I guess I just make a big deal out of it; I want to make sure my plants have the very best, since growing them outdoors where I live is only viable for a little less than half the year. Cultivation indoors is pretty much my only long-term option where I can keep them in conditions as close to their natural environment as possible. I might just have to buy a ton more lights, depending on what the meter will read.

Ferocactus wrote: ↑Mon May 17, 2021 2:44 am

mikethecactusguy wrote: ↑Sun May 16, 2021 11:59 pm Why does it have to be a big deal? All you need is a meter that will give you a reading that is close. You're not doing anything that requires a high degree of accuracy. Just buy a cheap meter and work at getting the light correct for the plants.

I guess I just make a big deal out of it; I want to make sure my plants have the very best, since growing them outdoors where I live is only viable for a little less than half the year. Cultivation indoors is pretty much my only long-term option where I can keep them in conditions as close to their natural environment as possible. I might just have to buy a ton more lights, depending on what the meter will read.

Perhaps a bit late here, but I'm considering buying several of these PAR light collectors (https://pronova.de/en/products/agricult ... ector?c=90). They display PAR and DLI. It seems pretty straightforward. On the internet there are tons of lists with the recommended DLI for certain plants. I think for cacti the recommended DLI is 20-25.

This meter is terribly expensive. Too expensive for me at least.
On the other hand, I think it's an absolute waste of money.
It seems to me that it is best to use the descriptions of how many watts per m2 you need and choose the height of the light source and the type of light.
I use the PPFD Meter mobile app, it is enough for a fraction of the price. And so you have to watch the plants and react if necessary.
But that's just my opinion

Andrzej1972 wrote: ↑Thu Dec 01, 2022 10:17 pm This meter is terribly expensive. Too expensive for me at least.
On the other hand, I think it's an absolute waste of money.
It seems to me that it is best to use the descriptions of how many watts per m2 you need and choose the height of the light source and the type of light.
I use the PPFD Meter mobile app, it is enough for a fraction of the price. And so you have to watch the plants and react if necessary.
But that's just my opinion

You're right, but I forgot to add that in my case I would be measuring natural light. For artificial light there are off course cheaper alternatives. I'm not planning to measure light several times a day in different conditions using an app or light meter. Too labour intensive and not very accurate. My suggestion was perhaps a bit out of context. My apologies for the confusion.

Give this app a try though, there is also a free version. With natural light, things are even simpler. The simplest luxometer, even a photographic one, is enough. I have panels without yellow light, and here is the problem with measurements

For anyone that comes back/across this thread, lighting doesn't have to be difficult.

Here's how to simplify it:

- purchase a lux meter (look up "LX 1010b" as an example meter that will work just fine. They're $20 last time I looked on Amazon. Nicer ones exist but aren't truly necessary.) I would advise getting one with a sensor that is attached by cord and not affixed to the top of the device. Just makes life easier

- Use it to measure *white* light only. It will not give you accurate readings for pink-white lights or blurple lights unless you know the CCT values for those specific lights.

- look up the color rendering index (CRI) value for the lights you're measuring. Most LEDs offered these days have CRI values of 80 while some of the nicer ones have CRI values of 90. The following conversion factors are to be used with white LEDs *only*. HPS lights and other older tech lights will have different conversion factors. Tbh, you should really be using LED these days because any other option (besides the sun) is unbelievably inefficient costwise.

- if the CRI value is 80, use the following conversion factor: 70 lux = 1 PPFD

- If the CRI value is 90, use the following conversion factor: 63 lux = 1 PPFD.

These conversion factors will get you PPFD values that are at least 90% accurate.

Excellent advice, I greatly appreciate everyone's input and experience!

I've moved to eastern Idaho about 1.5 years ago now, and have found more success in keeping the plants outdoors in the drier climate. I've been noticing much stronger spine growth in them as well, thanks to the UV rays in natural sunlight.

I suppose encouraging stronger spine growth is a bit of a challenge under artificial lighting conditions, though it certainly is doable.

Ferocactus wrote: ↑Tue Jan 31, 2023 6:01 pm I've been noticing much stronger spine growth in them as well, thanks to the UV rays in natural sunlight.

I suppose encouraging stronger spine growth is a bit of a challenge under artificial lighting conditions, though it certainly is doable.

Heavy spination is encouraged by intense lighting, either artificial or natural. The plants doubtlessly benefit from the bit of shielding the spines offer from UV light but UV rays aren't directly responsible for the production of dense spine production. Just high light conditions in general.

Glad you've had more luck since your move