What is HMI Lighting?

Kimberli

Kimberli

Member
Hi All!

I am looking to purchase some good, but decently priced, indoor or indoor/outdoor lighting. I was told HMI lighting is really really good, but can someone elaborate what it is and what kind of equipment and brand I should buy?

Thanks guys!
 
Kimi, My friend Sal says if I'm around to work on your production he's got 2 650's and 2 1k Arri we can use. I'm hoping to use them on my production. I'm also looking to get a Kino Flo Ring-Light for when running at night on the steadicam.

Oh and yeah, those HMI's are expensive!
 
Does anyone know how much more powerful an HMI is than a tungsten lamp? How many footcandles does a 1.2k HMI put out?
 
In general an HMI puts out about 3 to 4 times as many footcandles per watt than a tungsten lamp does.

Exact photometrics depend on the particular light -- an HMI PAR with a spot lens can deliver incredibly intense light over long distances, but in a narrow pattern, etc.

Plus, you also have to figure that HMI light is blue, not orange, so if you want to make a true tungsten-to-HMI comparison you'd also have to take into account the effect of gelling the light to make it comparable color. So in that case, it would take a 2,000 watt tungsten light with full CTB gel to match the output of a 150w HMI.

Or, a 400w HMI with CTO can deliver about the same output as a 1,000w tungsten fixture.
 
I just bought two HMI's from visual products.

Lee 1200w HMI Fresnel and 575w HMI Fresnel. Both with electronic ballasts. I am using them now on a feature and they are saving my life.

For day scenes I shoot them through the window and bounce them to bring up the room. Also for night scenes they double as moonlight. Exteriors they can fill in sun light etc.

Also they are much brighter per watt, so I can run my 575w which is more like a 2k tungsten along with a lot more lights. They are much heavier (junior stands) and need ballasts but they are worth the money.

A new arri HMI is too much but used HMI's are not that expensive. Don't get Magnetic Ballasts however.
 
Another thing to consider when making the Tungsten to HMI comparison is that footcandle for footcandle HMIs generate dramatically less heat than their equivalent Tungsten units. Especially when daylight balance is required. Put CTB on a Tungsten unit and you're pissing in the ocean. The sad thing about Tungsten lighting is that it's really an infrared space heater than happens to give off a little light... in other words, most of the electrical energy going to a Tungsten unit gets turned into heat. Given their daylight balance and cool operation and as well as their efficiency, in the scheme of things HMI lighting is not as expensive as it first seems. I've shot lots of projects with a majority of HMI lighting and we were able to move faster and stay cooler than if we had to deal with Tungsten units. Rental is the way to go unless you are going to be using them a lot over a period of time, the downside of HMI lighting is that it's high maintenance stuff.
 
HMIs do have their downside, that's true. Especially cheaper HMIs with magnetic ballasts. You usually have to wait a good 10 minutes or so for them to warm up, and you can't hot-restrike them -- if you turn the light off, you should wait several minutes before turning it on again... and magnetic ballasts are quite heavy. And some frame rates/shutter speed combinations will cause flicker at film camera speeds.

Modern electronic ballasts solve many of these issues, but are signficantly more expensive. A new 1200w HMI PAR system with electronic ballast is maybe $8,000.
 
My 1200w HMI runs cooler than my tweenie. Enough said.

However there is a considerable amount of work to keep the HMI working. The ballast, lenses, head cable, and just more connections leads to more headaches when something doesn't work. My tungsten lamps are very simple. My 1200w died mid shoot and it took about an hour to debug it, after the shoot.

Also the bulbs cost like $100 each. But I can hot restrike because of the electronic ballasts so no HMI explosions.
 
escozooz said:
there is a considerable amount of work to keep the HMI working
Click to expand...

Oh yes. That's why the way I see it, larger HMIs are the things I prefer to rent when I need them. Let the rental house worry about the maintenance. All I have to do is check the color temperature on pick-up to make sure they did not try to slip me a lamp that's long in the tooth (HMI lamps get greener and greener with age, that's why it's good to have minus green gels in your kit).
 
Do HMI's always require ballast? Do they always require a generator? If not, what is the largest size HMI you recommend plugging into a normal wall socket? I was on a shoot recently where we used a 2500watt HMI w/electronic ballast and a monster generator. The 100' of cable was about 100lbs by itself! We had a constant hum from the generator since we could only put the light 100' from the genny. What are some solutions to reduce that noise while still giving the generator airflow? Could you put some type of collar around the mic (like the ones you put on a dog to keep it from biting itself:) to cut out genny noise? It would have it's own shock mount of course. Does the ballast regulate the voltage keeping the 5.6k constant or is it just a safety precaution? Does the type of generator you use make a difference? Noob asking noob questions.

Thanks

-Kevin
 
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