[Konvas] DIY HMI lighting - off-topic

[Sean McVeigh]

Hey all,
As a bit of an experiment, I've been wanting to toy around with HID  
lighting -- the generic name for HMI <tm>.  And after Todd mentioned  
he had acquired a new HMI setup, I decided to give things a look.

The justification for this is that, well, on standard north american  
household circuits, you're really limited to tungsten fixtures under  
2000W -- and that's 2000W of very HOT light.  Well, I'm sure most of  
you know that there are much more efficient ways to flood a room  
(aside from using the big light in the sky) -- fluorescents are around  
4x more efficient than tungsten lights, but they are not very  
controllable, and, well, there aren't a lot of high-power options out  
there.  High-Intensity Discharge (HID) arc lamps give you a similar  
efficiency ratio (4:1), so you can theoretically pump out the  
equivalent of 8-10KW worth of tungsten lighting on a single household  
plug!

As a bit of a tinkerer, I thought I'd have a go at putting a system  
together.

A wee technical shortcoming of discharge lamps is that they are not  
continuous light sources.. very similar to fluorescents actually.   
They require ballasts to regulate the arc current, and naturally  
ballasts come in magnetic and electronic varieties.  While the  
magnetic ballasts are cheap and plentiful, they will flicker on film  
if you are not shooting at a safe framerate, and they are heavy.  The  
electronic ballasts either work with a low-frequency square wave  
(which yields a near-continuous output) or with a high frequency (like  
electronic fluorescent ballasts).  Oh, and these lamps typically need  
a few thousand volts pulse for ignition -- and some must be allowed to  
cool down for several minutes before re-striking them (non-hot- 
restrike).

Okay, with that bit of research done, and not wanting to design my own  
electronic ballast, I set out to try and purchase one.  Well, the  
cheapest 575/1200W ballast I could find was a used one for $1400...  
not a good start.  It turns out that almost no one outside of the  
cinema industry builds an affordable electronic ballast for 575 or  
1200W HID lamps!
All is not lost, however,  if you're willing to forego the standard  
bulb sizes of 575/1200W, there are a few interesting options out there  
for the do-it-yourselfer.  For those options, it appears that we can  
look to the aquarium and hydroponics crowd.  There are at least 3 or 4  
companies building electronic ballasts in 250, 400, 600 and 1000W   
ranges for very attractive prices targeted at these markets.  I ended  
up choosing one from Lumatek, as they seem to be located in Canada,  
and the ballast was a mere $175.   (so could buy several for less than  
the cost of one used 575/1200 HMI ballast!).

To select a bulb is a bit more of an adventure, and is really the  
deciding factor in the design of the rest of the system.  In fact, you  
really should select a bulb that meets your needs, and then pick a  
ballast, etc. after.  It turns out there is a lot more variety in  
discharge lamps than I would have imagined!  They come in many shapes  
and sizes, many CRI ranges, different colour temperatures, different  
socket types, different expecte lifespans, etc.
After a long read through all of Osram's offerings, I settled on the  
HQI-TS, which is a bit of a trade-off between the more expensive HMI- 
style single-ended lamps such as the HSR and HMI range (by the way,  
HMI is a trademark of Osram, and not some special kind of lamp.. it  
just became a household term -- like kleenex or coke) and the HQI  
range of single ended lamps with hugely long lifespans, but totally  
inconvenient sized packages (some of them around the size of a foot- 
long hotdog!).  The HQI-TS is about 8 inches in length, is a double  
ended lamp, and is expected to last for 12000 hours!  (compare that to  
750 or 1000 for the HMI and HSR range).  It has a nice high CRI and a  
daylight colour temperature.  The only downsides (aside from being a  
bit larger than the HMI/HSR) are that it has very poor UV shielding  
(not a huge problem, since I plan to use it in a soft box or in a  
closed fixture like a fresnel), and that it must burn in a horizontal  
position +/- 45 degrees -- not a huge problem, since most people don't  
typically roll their lights from side to side.  The big bonus with  
this lamp is that I picked it up for only about 45 Euros from diy- 
beamer.com (including the ceramic Fc2 sockets!).  Compare that with  
$200 and up for the HMI/HSR bulbs!   If the Osram brand name isn't as  
big of a deal to you, they sell a clone lamp for about 30% cheaper.

I was a bit nervous that I couldn't definitively determine if the bulb  
and ballast were actually compatible, but I decided to make the  
purchases regardless.  So after about 2 weeks of anxiously checking  
the mail, I now have everything needed to fire things up.   To my  
delight, it lit on the first try, and proceeded to get brighter and  
brighter and brighter and....  nothing exploded!!!

So, for $250 -- I now have the equivalent of about 1600-2000W of "hot"  
light in my basement breaking itself in.

The next step is to select a suitable enclosure for it.. I am eyeing  
old 2K mole fresnels and the like, but I need to figure out whether or  
not I can fit 9" worth of bulb and socket horizontally inside one of  
them  -- and actually, this was my main reason for writing this post:

	DOES ANYONE KNOW WHICH FRESNELS HAVE 9" OF CLEARANCE INSIDE THEM?

I could have gone with the smaller HMI/HSR bulb (only about 6" long)  
and used a smaller lamp housing, but I have a feeling that any savings  
in cost of a larger fixture would be eaten up when that first 1000- 
hour bulb burns out and I have to plop down $200 for a new one (vs $60  
for the HQI-TS).

Anyways... sorry for the lengthy email... Just thought I'd share a bit  
of the process with you... I'm pretty stoked that for probably around  
$500, a complete high-powered HMI-type lighting fixture can be built!   
I think I will make about 3 of them :)   And for the other keen DIYers  
out there, here are some links:

HQI-TS 400W/D: http://catalog.myosram.com/?it_p=4050300296401
HQI-TS 400W/D with Fc2 sockets: http://www.diy-beamer.com/EN/store/comersus_viewItem.asp?idProduct=276
Lumatek 400W ballast: http://www.lumatek.ca/proddetail.php?prod=400-120

Cheers,
Sean

(as a side note, I also picked up the $200 Alzo HID ballast and bulb  
(150W) to play with, and it so far has seemed rather fickle -- it is  
exhibiting some flicker, the colour cast is kind of purply, and it  
does not reliably ignite for me -- might be my socket setup though.  I  
can't recommend this system yet).