HPS Vs MH for flowering?

Zen · May 21, 2009

Hi all,

Sure, I know that it is 100 percent excepted that HPS lights are what one should use for flowering. BUT here and there I have come across threads where people have said that MH have given them better results than HPS bulbs for flowering. I didn't give them much weight because most of the books say that HPS are the standard for flowering. Recently I read Skunk magazine and the Rev wrote that he does not like HPS for anything and that the MH spectrum was better for flowering... thus the reason for this thread.

Can any of you cats who have flowered with both types of bulbs, HPS and MH, tell us which they have had better results with? I think it would be helpful for everyone if we got to the bottom of this based on the first hand experience of many.

:smiley_joint:

Pyro G. · May 21, 2009

Good question Zen, I definetly wanna know if anyone has tried flowering w/ MH. I personally have NOT. i'm curious too.

vindiesel · May 21, 2009

CMH has best overall spectrum output and is cooler running, but as powerful as an HPS or regular MH. i never flowered with anything but CMH, but i know i love what i see. CMH not available in anything over 400W i dont believe. maybe 600.

Jalisco Kid · May 21, 2009

I use a mixture and change as I go. I start under a 75/25 mh/hps. Switch over to a 60/40 hps/mh at week 5, then the last 2.5 weeks I am at 100% mh. Sats like mh more. Suerte JK

0sWizZle · May 21, 2009

CMH is the worst light u can use for flowering or anything cannabis related for that matter.... and according to Nasa the best mixed ratio of Red to Blue is 4:1 although i've read 3:1 also....

6500 Kelvin the first 2 weeks of bloom...then HPS all the way through...and if stretch isnt a concern of urs..then HPS from start to finish

l33t · May 21, 2009

I like both lights,

if I flower indicas or hybrids I use hps all the way for flowering if I work with sativas I like mixed spectrum or hps for most of the flowering and last weeks its MH only..

kansasgrown · May 21, 2009

I have flowered under both and definitely prefer HPS. Not too sure if it is the spectrum or if it is the lumens as the HPS has approximately twice the lumens of the MH.

l33t · May 21, 2009

a good MH light although has less lumens it will have as many PAR watts (perhaps even more) as an HPS of the same wattage but flowering cannabis plants its more than just photosynthesis.

HPS produces more bud and plants are less leafy imo while MH can produce a bit more frosty and more tight buds but it all depends on strain , some seem to show positive differences with the MH while other's don't.

jadins_journey · May 21, 2009

I've ran 1K MH, HPS and Dual Arc. The MH and HPS bulbs are in storage these days, the only light I burn is a Dual Arc (60% HPS & 40% MH) single bulb fired with a HPS ballast. You get the best of both worlds with this bulb. Granted it's more expensive and can blow early but my warranty is solid. Can't understand why more folks don't run these as they freakin' ROCK!!

jj

l33t · May 21, 2009

how is the penetration of the dual arc 600watter (or is it a 1k?) compared to a Hps or a MH of the same total wattage?

0sWizZle · May 21, 2009

those dual arc bulbs are garbage.....its basically a 600 watts bulb and a 400 watt bulb in one tube...meaning...u dont get the real light coverage of a 1000 watt bulb....theres not one solid arc in that bulb...theres 2...not as strong as one solid tube

jadins_journey · May 22, 2009

0sWizZle said:
those dual arc bulbs are garbage....

each their own my brother, my plants don't seem to mind..

jj

l33t · May 22, 2009

of course they wont mind :)

but did you do a side by side comparison test or measurements or are just saying?

I d love to try em out but if the penetration is less I would go with regular lights.

jadins_journey · May 22, 2009

l33t said:
how is the penetration of the dual arc 600watter (or is it a 1k?) compared to a Hps or a MH of the same total wattage?

The FootCandle reading on my digital meter is 23% less for the dual arc than with the HPS but very comparable to the MH and yes I only run 1K ballast. For me personally there is a trade off between intensity and spectrum of light. These are 2 different concepts of lighting that obviously some folks can't grasp as these bulbs have been recently called garbage LOL.

I'll trade a footcandle any day for a broader spectrum of light, the difference in the plants smell and taste are worth every single FC.

jj

l33t · May 22, 2009

Thanks for the input JJ

Its really nice to see you did some measurements.

So 23% less than a regular 1K HPS then..

So if they are not as good as a 1k light I see no reason why not use a 2 light combo , 400w MH + 600w HPS or 400w HPS + 600w MH

other than the need of 2 ballasts..I see no reason why one wouldn't go with two separate lamps , imo you can create much more uniform lighting with 2 hoods and make the most out of the wattage used.Of course with dual arc the different spectrums will be more blended but with more uniform lighting you can def get more bud.

Is there a really good reason why one would prefer a dual arc apart from the fact one would only need one ballast and one bulb purchase with this lamp??

PS

btw it would be nice if we could measure the light intensity at same distance you did the previous test with 2 lights/hoods one MH , one HPS (total wattage of the 2 being 1k) , just like I mentioned above and see how the results compare to the dual arc.

sdgrower · May 23, 2009

jadins_journey said:
The FootCandle reading on my digital meter is 23% less for the dual arc than with the HPS but very comparable to the MH and yes I only run 1K ballast. For me personally there is a trade off between intensity and spectrum of light. These are 2 different concepts of lighting that obviously some folks can't grasp as these bulbs have been recently called garbage LOL.

I'll trade a footcandle any day for a broader spectrum of light, the difference in the plants smell and taste are worth every single FC.

jj

You are right on here JJ. Lumens mean nothing to a plant. Lumens relate to how the human eye measures light. Plants use light differently than the human eye. Lighting requirements for plants are better measured with PAR value (i.e. Photosynthetically Active Radiation)

Imo the Philips MasterColor Ceramic Metal Halide HPS-Retro White bulb

provides the best spectrum available. The biggest problem is that they are only available in 250 watt and 400 watts. They do burn cooler than a typical hps bulb and I am able to place them to within 8 - 10 inches of the tops of my plants without burning them. To me temperature at the leaf level is more important than an arbitrary distance of how far away a light should be from the tops. Placing the light closer permits me to keep a high level of footcandles/lux hitting the leaves.
I switch to the 430 watt Son-Agro bulb for the final three weeks. This bulb helps with flower sizing but the resin quality, smell and taste is imparted by the Ceramic Metal Halide.

Just my 2 cents

Cheers!

l33t · May 23, 2009

Things are more complicated than that..
Yes lumens mean nothing to plants..but PAR don't mean everything either when you flower..

If I just vegged plants then I would care only about PAR watts.
And even then I would do comparison tests to make up my mind on a bulb. Its the only way to know the truth in practice.

PAR watts are watts from the light that can be used by the plant for photosynthesis.
But in what area of the spectrum are 'these watts' specifically?

If you have 2 different bulbs (different spectrum) that have the same PAR watts one will perform better than the other..cause their photons will not be in the same area of the spectrum, ie a photon in the red area of the spectrum may be more beneficial to the plant compared to a photon closer to the yellow spectrum in a certain plant species , even if it can be used with the same efficiency by the plant for photosynthesis.T
For example red light can promote stem elongation/growth and this is desirable in many cases.Or it may trigger other things internally in the plant.

So PAR watts are again only part of the truth.

I remember reading from a grower (Ot1) over another site that he did comparison tests and he found the Agro HPS from Phillips gave less yields compared to the regular HPS model from same brand ('HPS PLUS' I think it was). The test was with clones so quite accurate.
Anyway the point is plants need different light for different stages and RAR watts don't represent the truth when it comes to flowering cannabis and yields.

jadins_journey · May 23, 2009

Appreciate the discussion here guys, that's what makes the Farm stand out above the rest.

The little research project I did compared all 3 bulbs at the same distance from the bulb, total of 12 measurements per bulb over a 12 square foot grow area. Granted 2 ballast and 2 bulbs would obviously be better than a single bulb but I am building a system based on a GrowLab 120 and there is room for only one bulb.

To compensate for the lower output of this bulb I do what sdgrower does, I just lower the hood down a bit as lower output means lower heat levels. Not even going to debate Lumens and PAR values as those concepts really are above my understanding, I go with what my plants tell me and they have come to a consenious; they prefer the dual-arcs :smiley_joint:.

Peace brothers,

jj

l33t · May 23, 2009

''To compensate for the lower output of this bulb I do what sdgrower does, I just lower the hood down a bit as lower output means lower heat levels.''

hi JJfrom my understanding of physics the lower light output means higher heat levels not lower. (due to energy conservation laws)

sdgrower · May 23, 2009

jadins_journey said:
I go with what my plants tell me

That is the best advice right there. Every strain is different and has it's own preferences.

Cheers!
:animbong:

HPS Vs MH for flowering?

HPS Vs MH for flowering?

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