Newb question about lighting

Discussion in 'First Time Marijuana Growers' started by whitelump, Nov 23, 2014.

  1. I haven't started my grow yet but I'm about to get lighting and decided to do metal halide/high pressure sodium combo and I've done research on light coverage but if I need 1000 watts does that mean of each or total like 500 hps and 500mh or whatever the equivalent is or 1000 of each if I plan to use both the whole time veg through bloom also isn't it better to get a bunch of 250 watts and spread them out for better coverage for the bottom branches im planning on moving the lights around thank u to anyone that can help
  2. How big is your space?  1000w approx 60w/sqft, I guess you've got a 4'x4' tent?  Maybe 5'x3', something like that?
    You're right about having more smaller bulbs to give you better coverage. although four 250w lamps would be inefficient.  You could run two 400w lamps and be a little under, still about right on light per square foot front.  If you wanted a bit more you could run a 400w and 600w for your 1000w output, or just go ahead with two 600w for maximum overdrive.
    You'll find that two lamps cover the space pretty well, especially if you've got a 600w in there (is my assumptions about your space are correct)
  3. Lol I'm not really sure yet but I figured I would get 1000 watters
  4. Just in case but I'm wondering if I need 1000 of each
  5. Why wouldn't a bunch of 250s work well? It seemed like that would get better coverage but I Dont know I'm probly gonna do 2 auto flowers I want enough to get me threw till I can start the process again thank u for your reply
  6. Ha!  You were literally like "Hmm, If I were going to grow some plants today, I figure a thousand watts would do the trick!" and then you posted that in here.
    well it depends on how big your space is, if you had a whole garage then 1000w isn't enough, if you have a small closet then 1000w is too much.
  7. OK do I need 1000 metal halide and 1000 hpsodium for like 4ft by 5ft approximately
  8. Okay!  that's something we can work with.
    In a space the size of 4'x5', you're typically looking at 1000-1200w giving you very good coverage.  That's all at once.  If you had 1000w hps AND 1000w mh running at the same time, total 2000w running at once, that's kind of overkill unless you are really making everything else work and you have your systems sorted out well. It will also be really hot.
    The mh and hps bulbs, they are often described as "veg" and "flower" bulbs.  It's not strictly speaking like that, so you do not need to have both.  You can use just hos for the entire grow, most people do, and you can use mh for the entire grow though most people don't because they think the hps will give them fatter buds.
    So my suggestions for your 4'x5' space are:
    • one 1000w HPS lamp only for the entire grow, or
    • two 600w lamps, one HPS and one MH lamp both for the entire grow,
    • one 1000w MH for veg, and then one 1000w HPS for flower, changing the lights at the switchover (may need different ballasts or same ballast depending on equipment)
  9. Thank u that makes sence
  10. No such thing as too much light. Too much UVA/UVB, yeah. Otherwise, it's HEAT management that concerns you.

    Sunlight averages 128,000 lux/lumens (lux is lumens per square meter..effectively you can, and I do, work with lumens for the direct light hitting the plant, for various reasons).
    1000 watts of HID produces 92,000 lumens at the bulb.

    I put a corrected chart here, where I'd been screwing up due to missing a step in my math (classes regarding it were 10 years ago).

    You're not just getting the direct light...but reflective surfaces have inefficiencies, plus deal with fall-off between bulb and material, PLUS make the light travel farther from bulb to leaf, so they conserve some light that would otherwise never reach the leaves, but unless you want to do some ridiculous maths, don't bother.

    Use the chart....the listed percentage of the rated produced lumens is what intensity your plants get in direct light at the distance from the source.

    If you can produce the light, then all you need to be concerned with is heat management and footprint.
    A thousand watt MH during veg, switch the bulb to an HPS during flower.

    Reason being MH is heavier in blue spectrum. Blue wavelength light is shorter wavelength (about half that or red). so is more energetic. Sun energy plus nutrients plus water equals energy to grow. In veg stage, your plant is, effectively, "a growing kid". In flowering stage, it's "a pregnant adult". So it needs a "different diet". Longer, lower energy wavelengths, and less exposure to them (12 hours a day). And that's what HPS delivers...heavier balances of red wavelengths.

    For a 4' by 5', most hoods and lamp give you more than adequate coverage with 1,000 watts HID.
  11. Thank u so much everyone that helped a lot I also have mylar to hang up bubble buckets for dwc and general hydroponics flora series and Humboldt's secret golden tree nutes I guess I will do 1000 mh for veg HP's for bloom now what should the distance b to plants when their new baby seedlings? Would I b wasting way too much power for it not to b worth it using 1000 mh but keeping it far away or should I also get fluorescents or whatever i m not worried about price of lights I just want the best possible outcome I'm planning on eventually getting LEDs so my ? Is what's the best light n distance for seedlings
  12. You can use your MH for seedlings, but they need to be pretty far from them. Im not sure about distance, im sure indie-kah will chime in with better, more detailed advice. The dude seems like a lighting genius. I use cfls for seedlings and have good results. Youre going to save a shit load of electricity and you wont burn the seedlings.
  13. How many watt CFLs? and how many bulbs do u have chrontar?
  14. #14 Indie-Kah, Nov 24, 2014
    Last edited by a moderator: Nov 24, 2014
    Seedlings start in cold seasons, comparatively. Sunlight intensity is down and lasts for a shorter period. So the advice on moving the light away is good. Not TOO far away, but after looking up my initial screwups in math regards to lighting, the difference between 2 feet and 3 feet is so insignificant as to create no harm (at 2 feet it's 75% of what it was at 1 foot, which is 66.17% of what it was at 1 inch. At 3 feet it's 72.3% of what it was at 1 foot.

    Or, in real numbers...a 1,000 watt HID actually puts out around 92,000 lumens (lux, at a given point in surface, lumens is the "spherical" rating of 1 lumen i intensity at any given point on a globe around the source), so at 1 inch, it emits 92,000 lumens intensity, at 1 foot 60876.14 (calculations for a 1 inch /12 inch comparison).

    But that means if initial measurement is done at 1 foot, your initial reading is 60876.14, at 2 feet you "lose" 75% of that for 45657.11...measure that in inches instead, 39495.91 on the inches scale.
    These scales don't truly balance until you're talking significant numbers in comparison, truly, as your fall off by the inch or by the foot is progressively smaller (for instance, measure both at 10 feet, the effective light intensity reaching the surface is near equal. The only time this is really wonky is when using completely disproportionate kilometers vs meters, where your "wiggle room" is going to have a standard deviation of plus or minus two significant figures.

    Basically saying that there will be no real difference in intensity at six feet measured in inches and 6 feet measured in feet.

    Ideally, for a physics problem, your distance units are meters, but you CAN apply the chart to any unit of distance and come up with figures that are near accurate (plenty accurate enough, considering I disregard all reflected light due to secondary issues).

    Use said calculator, you know 1 foot is approximately .3 meters. 55,5464 lumens. 1 meter is 49,992
    Compare in inches, with a single inch being 1/12 of .3...result is a ridiculous number...but at that range, you're not getting as big a footprint, and, as said, lumens is the rating of total light energy given off in ALL directions. If ALL of that light intensity were to be focused on a single square meter, that's what you'd get. But only a portion of it hits directly on a surface. Technically, this is lux,. In practice, easier to calculate in lumens that reach the leaf (figure the leaf as one small portion of the surface of the globe used in measuring luminosity).

    Do the same in inches, across the board, the difference in figures is just 459061 at "33 inches" compared to "49,992" when measured in meters.

    Still a significant difference...of two significant figures (4.59061 * 10 to the 5th vs 4.992 * 10 to the 5th...the two decimals immediately right of the point change, two significant figures).

    Take it at 3 meters vs 99 inches, 5,555 lumens of intensity hit any single spot (5,555 lux if it covers a square meter, or an equivalent intensity at a given point)...or 5,555 lumens at 99 have to move out to 8 points past the decimal to see a difference.

    BTW, "lighting genius", definitely not...I went four damn days missing the same step in my math without realizing Had to get into an argument where I KNEW he was wrong, but he insisted *I* was wrong before I cracked open and old physics book and did a facepalm.
    At least I had the balls to apologize, as a result, and am trying to give corrected information.

    However, it doesn't matter how you work it, I actually ended up giving advantage CFLs in condemning them using the "mistake math" takes 20 of them at 12 inches to deliver the intensity of direct light a 400 watt HID delivers at 24 inches, not 18 to match intensity at same height, working an inch for inch scale. Meter to meter, same "2 significant figures", but the lack is STILL on an identical scale.

    Mylar, I HAMMER people for using...but it's opinion based on the fact that, though mylar is an extremely efficient reflective material, it was invented to reflect and conserve heat. If you have no hot spots, and good heat control, no big deal. But I haven't heard of too many people NOT having to overcome heating issues. So, IMO, it's an absolute no-no. If you have good heat control, or heat retention problems, you should think "oh fuck him", and do what you want with mylar.

    Sorry, but any material used to wrap around someone who fell through ice into sub-freezing temperature water while it's below freezing in the air, to bring their body temp back to safe levels on the quick-time through reflecting what heat they're producing THROUGH clothing soaked with sub-freezing water, or to attempt to shield wildfire jumpers who get cut off ("shake 'n' bake bags, they call them, and they DO work, to an extent) just doesn't strike me as a safe way to keep plants happy and healthy without massively effective heat control. Wonderfully efficient light reflection...but is the heat reflection and conservation worth it?
    IMO, no.

    Light intensity is almost never going to be an the surface of the earth, we experience an average of 128,000 lumens intensity/lux on the ground on average, globally.
    HEAT is the issue (and too much UVA/UVB/IR too close to the plant, since those are lacking to the point of non-existent in outdoor periods when seedlings pop).

    Outdoor grows deal with colder temps and light at a greater angle (tilt of the earth), which means marginally lower lux/effective intensity at the plant. So lower levels of light from your hood/bulb won't hurt 'em, if it's within reason, but midsummer intensities (18 to 24 inch hang) WILL, to some extent, and the associated heat DEFINITELY will. You could put a CFL or LED pretty much right on top of the plant, and not run that risk, but your intensity in comparison would still suck. And switching from seedling to veg is a "fast growing" process...moving from "crawler" to "toddler", in human growth terms. They need more energy, but nowhere near the amount a tween to teen in a growth spurt does. (Also known as "why my 5 year old brother eats about a tenth of what my 12 year old brother does, even though the 5 year old increases in proportionate size faster"--proportionate, not absolute, being operative. A 3 foot kid who becomes a 3'6" kid in a year grew about 15%, a 5'8" kid who grew to be 6'2" in a year only grew 9%).

    If/when you use the linked calculator, always remember, the lux rating it's giving you is the total light assuming a globe at the distance measured in square meters divided by the luminocity (lumens) at that distance, so the "lux" isn't going to be accurate for these purposes, except when applying it to relative intensity to a surface at that distance (if you have 5,555 lux as a figure, multiply that by the portion of a square meter the leaf represents, you have how many "lumens" actually hit that leaf at that intensity).

    It's incredibly involved to try and take all the variables into account and apply them circumstantially, so "quick and easy" for me is to calculate lumens, and work that as the energy the leaf receives in terms of intensity, and therefor maximum energy it has available to make use of.
    I don't really want to get into a discussion about it, but I am curious about your overall method.  You've made a lot of effort to be as accurate as you can, so when you considered the CFL-to-HID comparison, did you account for the fact that 20 CFLs actually spread the light source out over a large area, so one plant is getting both light from a very distant CFL and also light from a much closer CFL, even though the "distance-to-source" is actually considered to be equal?
    If you modelled the CFLs in groups of 4 (many people use two splitters to make a cluster of 4), so one set of 4 bulbs is calculated as 12 inches, then the next two sets of 4 bulbs probably 7-8 inches left and right of the first one so they're actually about 14 inches away away from the same point, and so on.  So that being the case, how many CFLs do you need now, and how much of a difference is it between a plant in the middle of the room and the edge of the room?
    In a similar vein, how does the difference work out between one 1000w HID that has to be 24 inches (or whatever) away from plants, and two 400w HID bulbs which can both be that much closer because the heat source is dispersed?  Where is the crossover point?
    You have obviously already thought about the topic enough to appreciate these questions.  It's the kind of thing I would work out myself but I'd be starting from scratch and I've got chemistry to think about instead of physics  :smoke:
  16. #16 Indie-Kah, Nov 24, 2014
    Last edited by a moderator: Nov 24, 2014
    Easy answer to that is "no". I've worked consistently and for simplicity's sake, at direct light from bulb.

    The calculator page I posted has a section for calculation intensity per bulb at a given distance and angle (discard inefficiencies, you have reflected light intensity) if you want to do repeated calculations to come up with what would arrive if not impeded by other plant matter, but let's face it...your bulb on the far left isn't getting much light to the plant on the far right, because the plant surfaces between the two "capture" that light, and cast shadows, preventing it fro reaching the plant on the right.

    In practice and theory, you're right, that DOES have an effect. For simplicity of calculations/mental pictures, it just causes headaches if you don't want to set up a calculus problem on a graphing calculator.

    Dunno about you, but if I don't HAVE to do it to make something work, I avoid calculus based like the plague. have to use them in engineering. Doesn't mean I like 'em.
    I have 4 26w 5000k cfls on two splitters and I put about 4 seedings under them. I only have them under there for the first 2 weeks, and they're just in little starter plugs so they're close together. You basically want the seedling to be completely covered by the bulb.
    And indie-kah, you're a hell of a lot more knowledgeable than me about it. I absolutely hated math and science, im just not good with numbers like that.
  18. Numbers are numbers. Dunno why, but they kind of "speak" to me.
    But I know what you mean...I have a cousin who's a lumberjack, believe it or not. You use algebra and trig in that industry daily and almost unconsciously...put "a real algebra problem" in front of her, she panics, and can't do it to save her life.

    Numbers, used right, with the right formula, give you precision. Or the ability to estimate more closely, if "shortcutting" and simplifying processes.
    Even using "wrong terms" for simplicity (for instance, 1600 lumens at the bulb, done properly is 1600 lumens at the exact point the specific wave of light hits the surface, no matter the distance. Lux refers to the intensity created because light "diffuses". But for practical purposes, if you haven't noticed, I use the word "lumens" as a designation, because the accurate figure in lux is IMPOSSIBLE to calculate over sq meters of actual plant material light hits at so many different distances from emitter, reasonably. So call it "lumens hitting the top of the plant", and it illustrates perfectly well for mental image purposes. You'd do just as well to calculate surface area of the plant by calculating surface of a cone, averaging it for distance from light, and using "lux" at that distance. But it's more involved and difficult).
  19. I think you mean accuracy.  How long is my laptop?  I could be very precise and say 12.5471524342 m long (very precise down to the nanometre but very very wrong), or I could be much more accurate and say 0.4 m (only to the nearest decimetre but much much closer to the real answer)
  20. Nah, I meant precision, though you're right about scale being important. Used to working with things that have to be "precise to the millimeter", though NOT "precise to the micron".

    I suppose that could be referred to as accuracy, just not the way I'm used to thinking about it. Terms I usually use, "accuracy" has to do with how well I put a bullet or arrow where I want it to

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