Led light ....

So I have just changed from a 250w hps to a Spider Farmer Sf2000 pro unit ,

My tent is 60x60x120cm

18inches from canopy what should I dim the light to ?

I already see some bleaching to leaves.
Tia.

@ 150W your LED should produce close to same amount of light than the 250W HPS.
So around 3/4 of max power?

Have you checked out the Photone app for measuring the amount of light?
It's pretty handy for getting an idea how much light you are throwing at it.

cage said:

@ 150W your LED should produce close to same amount of light than the 250W HPS.
So around 3/4 of max power?

Have you checked out the Photone app for measuring the amount of light?
It's pretty handy for getting an idea how much light you are throwing at it.

Click to expand...

It's a 200w led ,

At 80%

markrossiter11111 said:

It's a 200w led ,

At 80%

Click to expand...

So because hps is less efficient, roughly speaking, the hps was delivering only about 125 watts to the plant, whereas the 200w led is delivering much closer to 200 watts, because it's roughly 90% efficient (hps is like 60% efficient)

I think you'll find a lot of people recommend dimming way down. I have a different light, but i start flowering at 40% power, and 24" above the canopy.

as you increase feed during flower, you can lower the light and increase power accordingly. but yeah don't blast them starting on day 1. they won't be able to keep up

MtRainDog said:

So because hps is less efficient, roughly speaking, the hps was delivering only about 125 watts to the plant, whereas the 200w led is delivering much closer to 200 watts, because it's roughly 90% efficient (hps is like 60% efficient)

I think you'll find a lot of people recommend dimming way down. I have a different light, but i start flowering at 40% power, and 24" above the canopy.

Click to expand...

It's difficult isn't it because they say 12 to 18 inches above the canopy ,
But in a tent no light Is lost so I guess it could be higher ,

My main fear is Lightweight non dense buds ,

What is your light and space size please ?

Thanks

markrossiter11111 said:

It's difficult isn't it because they say 12 to 18 inches above the canopy ,
But in a tent no light Is lost so I guess it could be higher ,

My main fear is Lightweight non dense buds ,

What is your light and space size please ?

Thanks

Click to expand...

3x5, hlg 350r

12-18" is where I like to end up once I'm running full blast.

but starting out, in the first couple weeks, the plant is changing. It will happily take more feed and more light, but you gotta be gradual about it. lights too far and you'll get some over-stretch, too close and you'll fry them. same with feed. too little and they'll go pale, too much, fried. etc.

also, it depends on how big your plants are when you begin flowering, how you've trained them, medium, containers, etc. lots of variables, but gradually upping all their inputs is a safe bet.

So first thing I'd do is shoot for 80 degrees fahrenheit in veg.

Personally If I veg with my leds I run them about 25- 50% power @18" distance.

I find my plants are happier like that, they don't show any red stems, or signs of stress.


Then crank them up to 100% the day I flip to flower.

That's just low tech trail and error of my own and many others combined experience growing since these new highly efficient white spectrum lights came out.


But if you want a different and more detailed perspective then perhaps @Delps8 can chime in.

40% is as low as my 760watt LED goes but I have it mounted about 24 inches above. I usually go by DLI. I make sure for seedlings I am around or so 20 DLI. As weeks go by I adjust upward weekly until Flower where I usually push my plants to the 55 DLI limit using no CO2

Attached are two charts I usually go by, one for Photo periods and one for Auto flowering. These are pretty close to what I have always been told.

My Dli flicks between 50-54 ,

So should be ok

Also PPFD at 810

Re. dimmer settings and hang height - right on the manufacturer's product page. As is common with manufacturers, their guidance is conservative but this is more conservative than Mars. Their guidance will tend to be conservative because their goal is for you to have an excellent crop rather that you have a very good crop as long as you don't call for tech support or bad mouth them. (I wrote software for Apple for a few years and got some insight the tech support issue).

Photone—it can be accurate or it can be quite inaccurate.
If you use Photone, you should be using a diffuser (22# paper) or buy the diffuser from GLM.com. Also, make sure you've chosen the correct spectrum/light type in the settings window.

Seeing that there's a PPFD map for your light, you can do a "soft calibration" by putting the phone on the floor of the tent when the light is at various hang height and dimmer settings and comparing the Photone reading to the reading in the PPFD map. That should get you close enough.

"A light meter will tell you how much light is falling on your plant but only a plant can tell you how much light it can use."

In terms of how much light, a key point is the maturity of the plant. My belief/hypothesis is that the ability for a cannabis plant to process light mature by week 5 or 6. I say that because that's about the time when the vegetative state ends and one of the purposes of veg is to boil the infrastructure and processes that the plant needs for flowering (yeh, very obvious but it's a good place to start) and because I routinely grow my plants, autos and photos, at >=1k and I feed them that much light but about week 5.

markrossiter11111 said:

It's a 200w led ,

At 80%

Click to expand...

These settings use a conversion factor of 0.0175 which is extremely high. I use a dedicated flower light (LED) and it's not that high.

Attached is a document I wrote to help growers convert lux to PPFD and no LED has a factor that high. A 3100° CMH (whatever that is) comes in a 0.0170.

Lights that have more red in the spectrum use a higher conversion factor because they generate more PPFD for a given amount of input energy. Conversely, if there's more blue in the spectrum, which we see in veg lights, the PPFD isn't as high because blue diodes are less electrically efficient.

Your light has a lot of blue in it so I'd use a conversion factor of 0.0145 or 0.0148. The number may not be very important. It just depends on what you're hoping to accomplish by using a light meter.