Flaming Wasnt nessecary at all, i agree fully with Grizzly. With that said, i have to put in my 2 cents. I use both Digi Ballasts, as well as Magnetic. I have two 1000w Magnetic ballasts, and i use Sunmaster HPS bulbs, aswell as AgroMax 1000w MH Conversion bulbs. The MH Conversion bulbs work amazingly well and ive been using them for about 6 1/2 months so far. Theyre performing extremely well, and my light meter says that they havent deiminished in brightness at all. In comparison to a brand new standard MH bulb, i would say you lose very little by way of lumens if your going to use a Conversion bulb -- as long as you make sure your not buying a budget bulb. Agro is a reasonably priced bulb, its not the most expensive you can buy, but its also not even close to bottom rung. I would use AgroMax MH bulbs any day. HPS is another story though, lol.
As for Digitall ballasts -- Most Digital ballasts your going to buy are Switchable ballasts. Meaning that you DONT NEED TO USE A CONVERSION BULB in order to use both MH and HPS in the ballast. Thats one of the main attractions of going digital IMHO. If you are buying a digi ballast thats not switchable, then your better off going magnetic IMO, because its a waste of money.
Now LondonDZ,
If you have money for TWO lights, then pick yourself up TWO Switchable digital ballasts. Theyre about $50 - $80 more expensive than a regular magnetic ballast, but if you go Digital, then youlll have two fully functional switchable lights, meaning that you wont have to only use one for each spectrum, you can use MH in both during veg, and have twice the space to grow with. OR, you can always put one MH bulb in one ballast, and one HPS in the other ballast, and run both spectrums at all times. This is the best of both worlds, and you will see amazing results. Ive seen grows where the grower uses both spectrums in HUGE grow rooms. The plants under the HPS lights are nice looking, and the plants under the MH lights are nice too - but the plants that are caught under the spaces where both spectrums are mixed are Effin amazing looking. More frosted in trichomes, bulkier in some cases, and just over all looking healthier.
Think it over man, but take into consideration your ventilation also. I dont know what your budget is like, and i dont know what kind of equipment you already have, but if your buying your first growlights, maybe your better off buying one Digital Switchable ballast, hood, and bulbs, and then spending the rest of the cash on Ducting, a Blower, and intake and exhaust fans. Make sure you have proper ventilation for your growspace, its just as if not more important than your lighting is.
Hope that helped a bit. Good luck with your grow.
N stop the damn fighting. Damnit.
-K1.