metal halide and ballast
 

http://www.progressive-growth.com/pr....php?prod=4010

Has anyone ever tried these for photography use? They claim some of the bulbs are daylight balanced, more or less.

I haven't tried that particular one but I'm in the middle of experimentation with this for products for my company. I looked over their bulbs and the term daylight balanced is a bit of a misnomer. If the company doesn't list CRI at all its usually pretty low. The will be in the 65 to 75 range many times and that's just too low especially if you're doing film photography which you may be. You can send an email to the company asking about CRI but I doubt they'll even know what it is. It's just not an important spec to plant grow light companies.

As for the ballast, if may be a good deal but they don't even talk about whether its electronic or magnetic. The most important things there to ask are: is it electronic and what is the output frequency. Again, they don't list that because its not important to growlight people. This of course will control whether you see a flicker on your camera or not and possibly will hear a hum or buzz too at lower frequencies.

At the prices listed I doubt it would be interesting for photographic quality light. I've tested some of the grow lights and the light is definitely of a "green" quality. On the other hand, I've found some higher quality ballasts and bulbs that are close to Sylvania HMI specs. I'll be updating my blog with some articles on this soon.

mag and electronic ballast
 

They say the CRI is 90 on the daylight bulbs which are about 5000k

No info on frequency of ballast.

Hmm, when I looked I didn't see any CRI info at all. Well if thats true you've got a winner there. And the price is not bad either.

Why not write to ask the frequency on the ballast? Its probably okay if its electronic but it never hurts to ask.