Lumens, Lux, and Adding It all Up

Discussion in 'Indoor Growing' started by ceestyle, Jun 19, 2008.


    wietefras Well-Known Member

    You would need to measure the light exactly the same way every time to figure out if the light is diminishing. Not an easy thing to do.
    Skunk Baxter likes this.

    JayStrainHunts New Member

    Right This might sound extrely stupid but I am new to All this lumun stuff
    I have 12W Cfl would it be enought to start of an auto??

    Cannacat Well-Known Member

    I've tried really hard to understand all I've just read but my mind just does not work like that adn I can't work it out so I'm really sorry but I'm just going to ask.
    I have 2 600w hps lights, are they going to be enough to get my 11 white widows through flowering or should I add more? I also have a 2 lamp T5, am I going to need that in there with them too because I could really do with that to veg my new clones under while the girls are using the big lights.

    kmog33 Well-Known Member

    Depends on how big your space/ the plants are. With 2x600s you can grow 2-288 plants in a 4x8 ime depending on your grow style. 2x600s is a lot of light. 3 pounds wouldn't be too much to expect with a good yielding strain and the system dialed. 4+ once you really have your shit together.

    Sent from my iPhone using Tapatalk
    Abiqua and Cannacat like this.

    Cannacat Well-Known Member

    Hahahaha thanks so much for your quick response, you just made my day! Just did some quick maths and that'd be like a good year's worth of medicine haha :bigjoint:I can't give you the exact measurements cos it's just something we threw together and added to bit by bit, but I'm happy that the light is being fairly distributed between the girls; I do think I can improve on it further by making it more reflective in there, but I'm working on it.

    since1991 Well-Known Member

    Par meters are ideal but pricey. I have a digital footcandle meter. Iam used to lumens. Does anyone know the conversion of footcandles to lumens for this device? I assume it is x10,000???
    Abiqua likes this.

    Abiqua Well-Known Member

    since1991 and sanjuan like this.

    sanjuan Well-Known Member

    I set up my first COB grow and adjusted the luminaires for 5000 foot candles at 20 inches (as measured by a Hydrofarm digital meter).

    I turned off half the COBs for seedlings but they seemed to be stretching so I turned all the lights back on. The seedlings are now getting 3000 foot candles which I suspect is too much.

    This post is from DesertGrow89 in August:
    "Yeah start with a low light intensity, around 600-1000 foot candles for starting seedlings is great, two weeks later I like to increase it to 1500-2000, and progress to 5-6000 fc gradually."

    Does that sound about right?

    RangiSTaxi Active Member

    Phone lux meters work fine, download a app, google store( light metre app) many to choose from. ive used even with blurpurple led,

    veg 20000- 28000 lux any light source

    40000 lux blurple for flower

    48,000-58,000 lux HPS and cree 3590s budding at tops

    dont go over 58,000 lux, or you will get chlorophyll degradation.

    you will need a smart phone with a light sensor phone, like samsung S5 or above, clean phone lense and find the weak spots, adjust light for best even lux level across canopy.

    dont try flower below 28,000 lux on any light source results will be below average
    Last edited: Apr 5, 2017

    Wildoafi33 Member

    Good post

    Critical420 Member

    Here's a great way to determine how close should you place your lights to the plants. Take your lumens meter outside on a hot 85-degree day and point the meter up to the sun. Whatever that value is on your particular meter can be used to determine how close to place your lights above the plants.

    Craigson Well-Known Member

    Sorry way too much to just scroll and read through. And search brings up way too much.

    Whats the best k rating for HPS in flower?
    I ordered 2x 600watt hps and they come with 2100k bulbs.
    If it matters I will also have my 315w cmh which I have both a 3000k and 4100k(could b off by 100) bulbs so I can use either.

    herballuvmonkey Well-Known Member

    Craig the color temp is fine as I run 600s with 2000k Apollo horticulture bulbs and haven't had a prob except they degrade pretty quick. Maybe 2 grows out of em before they gotta go. Get yourself a lux meter (Amazon approx. 20 bucks) and hold it at the tops of your plants and it will give you a lux rating so you can tell when its time to change out your lights. This also depends on the size of the growing space so take that into consideration., If you wait til they start to look dim its too late.

    herballuvmonkey Well-Known Member

    Not trying to sound like a douche but I dont think that is correct. 100K lux is approx. 9200 lumens per sq foot. I flower at 90K lux with no bleaching or problems. The power of the sun is 10k lumens per sq ft so I try to stay close to that. It is easily accomplished with a 600 watt hps in a 3x3 tent. Running this and a scrog normally get ..5 to .6 grams per watt (300 to 360 grams for 1 plant).

    herballuvmonkey Well-Known Member


    Tim1987 Well-Known Member

    I hate to bring negativity to this thread, and disagree.
    But lumens is just how bright light appears to our eyes. Lux is just another measurement of lumens. Lux, is a measurement of lumens intensity of an area. I'm pretty sure one unit of lux, is equal to one lumen per m2.

    Plants don't see light. They only absorb PAR (photosynthetically active radiation). If you don't have a PAR meter, you're guessing.
    t917q and since1991 like this.

    since1991 Well-Known Member

    Yes. True. But if all you have is a lux/footcandle will suffice. Plants see par and those are the meters you want but they are spendy. If all you got is a regular ole footcandle meter..and you see bulb degradation or consistent reads..if pretty safe assumption that this correlates to PAR as well.
    cogitech, OneHitDone and Tim1987 like this.

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