Hmmmmm now you have me thinking....I hate it when that happens.

OK, one question then:

my pfo 400w mh ballast (tar style, $240) is not going to run my $150, 10k ushio bulbs as effectively as the pfo 400w mh ballast (hqi style, $380) will?

Also, I remember reading that the 250w DE pendants will put out more light for less wattage (ie, more light for less hydro bucks) then my tar style ballast and SE mogul bulbs. I was honestly considerging dropping my SE bulb setup for the 250w DE pendants (I am also having problems getting the bulbs in my current setup to fire every morning. I think the socket sucks)

Now, to actually add something to the thread, I am gonna go find the lighting thread on RC and link it :)

Different story here though. The "HQI" ballast that Steve refers to is only available in 250W. There is no "HQI" equivalent for 400W, what we have here is another place the term is used but not really correctly. The "HQI" in the 400W ballasts is a "Son Agro" ballast for sodium lamps that happens to work for halides. It is actually 430W not 400W so it overdrives your lamps ever so slightly. So .. they'll burn brighter, yes, but "more effective" or "less effective" is a subjective, qualitative call ... if by "more effective" you mean "brighter" then yes it's more effective but there has to be a downside somewhere, shorter bulb lifespan perhaps (also open to debate? .. not sure).

I think this is also open to some debate. It probably depends a great deal on the reflector you use. Personally, I think that average 250W DE's with an average reflector are probably as useful as an average 400W SE with an average reflector (except it takes 150W less to run). That's my unqualified, unquantified guess as an opinion... Meaning, probably if you look at different reflectors in different situations you may well get different results. But to me, given the choice, between running a bunch of 400's versus 250's .. I look at my powerbill and that's when I say I want to switch to DE's one day too .. just a matter of saving up some $$$ in the meantime.

Tony answered your first one for me :mrgreen: the only real HQI are 70 watt, 150 watt and 250 watt. but I see there is a 400 watt HQI bulb by Sylvania now so I am going to look and see what they are using to drive it.

OK the second one. no :mrgreen: the test that showed the DE 250 watt bulbs putting out lots of light was flawed. they used the reflectors and the DE reflectors are smaller and able to concentrate more light in a focused area. all the bulbs they compared them against (SE types) had no reflector. so it was a bogus comparison. I did a test with SamW's DE in the pendant against my SE under my reflector, I got almost twice the output at 12". now this is also misleading as he was driving it with the Icecap ballast (which under drives MH as almost all electronic ballast do) and also for the fact that I believe my reflector had a higher reflectance value than SamW's. I want to do some direct comparisons in equal situations in the near future, but I have to buy a third HQI ballast first and build a test box where I can test them with out reflectors or shields.

I will put out a request for old bulbs of both DE and SE types (250 watt only) to test out put of aged bulbs also as a comparison. Also if someone is giving away or selling real cheep different ballasts I would like to get a hold of those also.

if you think back there was a 150 HQI test that Sanjay did showing it had more out put than a 400 watt Iwasaki, this was a factor of the reflector on the DE bulb only so yes you can get a very high output from a DE set up but it will only be focused over a small area not spread out like a SE bulbs will.

as for the more light for less wattage this is also false. if I hook up a DE bulb to my M80 ballast it will have the exact current draw as my SE bulb. as for less heat that is a factor of the pendant housing only nothing to do with the bulb and you can buy pendant housings for SE bulbs.

Steve