whats the difference between MH and HPS bulbs???

Ok as a newbie I am concerned about not having enough light when it comes time to flower. I'll be damned to do all that work and flourecents not flower the plants to maximum yield. So heres my question. What are going to be the differences in metal halide and high pressure sodium? What different results do they have on the way the plants flower? Is one hotter than the other? This will be a big investment and I want to make they right choice. I need a ballast, chord, and socket. I notice there are ballast made for MH or ballasts for HPS. So I assuming you couldnt use a halide bulb in a hps ballast or vice versa. I think both bulb types will do the job but really want to know the nuances in growth differences between the two types. I have a 1000 hps bulb but dont only plan on 2-4 plants. However if the more light the better yield, maybe I want to just get the 1000 watt hps ballast and blast them with light! I guess it only means more yeild. My space is 2deepX5wideX5feet high. What wattage and bulb type would you suggest veterans?

MH = Metal Halide
HPS = High pressure sodium

Metal halide bulbs deliver a bluer spectrum of light suitable for vegative growth,

Where as sodium is more suited for flowering. you can veg under sodiums however the result would not be as good as it would be if you vegged under a metal halide.

Yes generally different ballasts are used for each, but you can get ballasts which will operate both.

I use a grolux sodium bulb which is altered to give more levels of the blue spectrum making it suitable for both vegetation and flowering. see my thread titled "my setup" in this section of the forum.

and i would have thought a 400W would be ample

hope this helps

Thanks well I cant afford a flourecents for vegging, halide, and hps. So I thnk Ill go with a hps. 400 aounda good 600 might be better as it will only mean more light. Where can you get these dual ballast that run halide and hps bulbs? Thanks for the advice. Everyone else feel free to add yours.

400 would be great for 4 plants,600 would border on overkill.to get the max light to the plants,make a devider to cut your room down to just big enough to fit the plants(say 2x3), a piece of heavy cardboard painted flat white would work.