I was given several 4ft fixtures from a tear down along with quite a bunch of tubes both T8 & T12s. All fixtures are 3 bulb. Some have T12s some have T8s and some are a mixture.
This all sounded like a pretty familiar tune, until you got to the part about having BOTH T8 and T12 tubes in the same fixture. That is decidedly odd, and probably far from ideal for several reasons. At the very least, you should check the ballasts in those fixtures to make sure they are "dual rated" for both tube types.
the T8s all appear to be 32 watts and theT12s 40 watts.
That's fairly normal; but the F40T12s are antiques, which are not even made any more (tho' some remain in the distribution chain, as of right now). Odds are that before long the best you're going to do in terms of replacement tubes is the so-called "Energy Saver" F34T12 types.
Will the12s & 8s have equal light out put ?
No. Not even close.
A typical F32T8 tube will produce about 2700-2800 lumens (some high-output variants will go significantly higher), on a nominal 32 watts; and after they age, they'll lose maybe 5-10% of their initial output.
Meanwhile, F40T12 tubes vary somewhat; but these are typical:
http://www.1000bulbs.com/product/6348/F-40T12DX.html
Lumens (Initial): 2180
Lumens (Mean): 1770
http://www.1000bulbs.com/product/4660/F-40T12DXALTO.html
Lumens (Initial): 2325
Lumens (Mean): 2025
Note that not only do they use more power to put out less light, they also degrade more severely over time.
The more common F34T12 tubes are even worse:
http://www.1000bulbs.com/product/6346/F-40T12CWXSS.html
Lumens (Initial): 1925
Lumens (Mean): 1656
Still using (slightly) more power than an F32T8, but producing MUCH less light.
What should I do to maximize the light per unit.
Throw them away and buy better lights?
I'm only half kidding. Those old T12 fixtures & tubes were free for a reason: They are essentially worthless. The T8s MIGHT be salvageable; but I frankly would not even waste my time installing the T12s.
I do realize that bulb color will make a perceived difference . All the bulbs I have seem the same.
But what, exactly? This is another area where old T12 stuff tends to fare VERY poorly by comparison to more modern stuff.
They also have plastic dimpled light defusers in the fixtures. Good or bad?
Depends to some extent on the particular fixture, and to an even larger extent on how they will be used and in what sort of environment. Fixtures with diffusers are generally better for relatively low-ceiling applications, where the lights will be mounted below perhaps 10-12 feet or so. If you're mounting the lights higher than that, you probably don't really need the wider light distribution such diffusers produce, nor the impact protection they can provide. You've told us NOTHING about your application, so it's anyone's guess.
Any education will be appreciated
Consider what can be bought for about $22:
http://www.lowes.com/pd_163697-337-WP232RLU_0__?productId=3181895
That's actually a pretty nice piece, with a Residential-rated (i.e., low EMI/RFI radiation) ballast; and the two F32T8 tubes it uses will put out about the same amount of light as THREE F34T12 tubes (more, after the tubes have aged), while using only about 60% of the power to do it.
T12's are pretty cheap if you're on a budget.
NO WAY.
Look at the examples I cited above. F32T8s are even cheaper, starting at about $1.50 each (cf.
http://www.1000bulbs.com/category/f32t8-fluorescent-tubes); but that is beside the point. The problem is, you need three F34T12s to get roughly the same light output as two F32T8s, and so you will be using more than half-again the electricity in the process.
THAT is the "killer"; because in ALL cases, the operating costs utterly swamp the purchase costs of the tubes AND the fixtures, in the long run.
Something funky is going on here. First, when I look up that exact model number (C 2 96T8 120 GEB) on the non-Canuckistan HD site, I get:
http://www.homedepot.com/p/Lithonia...ip-Fluorescent-Light-C-2-96-120-GEB/202329356
Which, as you will note
IS a T12 fixture. It would appear that one webmaster or the other has screwed up.
But it really doesn't matter, because in EITHER case, the fixture in question would be a pretty horrible choice.
At $40.78 (US price), it's not particularly cheap. See above for what you can get for about half that.
But far more problematic than the initial purchase price are the tubes required. Depending on which web site you believe, that's either F96T8 (cf.
http://www.1000bulbs.com/category/t8-single-pin-instant-start-linear-fluorescent-tubes/), or F96T12 (cf.
http://www.1000bulbs.com/category/f96t12-fluorescent-tubes/). Either way, they're horrid: At about 96 lumens/watt, the F96T8s are slightly more efficient than standard 4-foot F54T5HO tubes; but that's where the advantages end. They remain significantly more expensive, and a real PITA to safely transport and store without breaking them (not to mention disposal). And having to switch on eight feet of light at a time makes for inflexible switching schemes.
The F96T12s are also expensive and difficult to deal with; but as an added bonus, are MUCH less efficient (about 58-60 lumens/watt).
