HMI lighting vs Tungsten

I'm very curious about the use of HMI as an alternative to filtered

Tungsten in the studio and night location, basically anything non-

flash. I heard that HMI light is a lot stronger than tungsten. My

questions:

 

Does this mean that a 500watt HMI will give more light than say a

2500watt tungsten?

 

I use a 2500watt tungsten with softbox and blue gel, and get only

about 1/30 at 4.0 with 100 asa at 2 meters. How much HMI watts will I

need to get 4 or more stops light than this? and can I use a softbox

with it?

 

Can anyone recommend a good least expensive possible HMI kit(like 1

main softboxable/reflectable head and 1 fresnel hairlight for fashion

use) that will give me at least 4 or 5 more stops than the tungsten I

use above? and can I use a normal gasoline generator like I do with

tungsten?

 

Any advice greatly appreciated, thank you

Tiago,

 

Check out http://www.mole.com, go to thier lighting products, and do a search for HMI. Their specifications sheets give you foot candles at x distance type ratings so you can figure out what their lights will do.

 

Currently you are getting about 150 Foot Candles (FC) out of your current lighting .. and you want about 2500 FC. Their 4000 watt unit will generate that kind of power (lighting about 8 feet in diameter). The cost of the unit is about $1 per watt. Perhaps somebody can recommend somebody that is cheaper.

 

Ken

HMI is about 5 times brighter than halogen lights (I assume that

is what you are talking about, not tungsten) it is also usually

about 5400-5500K , or photographic daylight (5400K), so right off

the bat you'll gain 2 stops from not needing a CTB gel on the

light. You could also switch to a 3200K balanced film and

immediately gain those twoi stops blocked by the CTB, so say

you are shooting chromes and use Fuji 64TII (a terrific film, BTW)

and pushing it 1/2 stop to get an an E.I. speed rating of 100. You

are now up to 1/125 at f/4.

Switching back to the HMI solution, using a daylight film, you'll

need something in the range of a 2K to 2.5K light. Not cheap. As

a matter of fact it'll be more expensive than a decent flash

system, since electronic flash is in the 10-20x range more

efficient (watt/second vs. watt rating) so something in the 1000

w/s to 2000 w/s range will be useful.<P>But then using flash

isn't as trendy as using HMI.

Thank you very much Ellis and Ken. What's the story about 'ballasts' with HMI? Are they indispensable or could you just connect a HMI light to a normal gasoline generator or home power supply?

You must use the ballast with HMI - It is essential, and that's where most of the costs come in. HMI uses uses very high frequency ballast to provide flicker free operation on movie sets and TV productions. The exact ballast you need depends on the intended use. Most HMI manufacturers can provide guidence, as can most reputable TV or Film rental houses. You should also be aware that HMI calls for some careful precautions if water is to be used on your set - there is enough voltage to do serious harm. You will also need to ensure your available electrical systems are able to support the amount of current you will be drawing. This is the same sort of issue you face with normal Halogen instruments. Also, consider the fact that you will want high temprature accessories (soft boxes, etc., they cost a bit more than the strobe equivalents. Continuous light is great, but it cost a bundle over strobe (at least HMI does).

That's worried me now Cecil. I plug in a 2500watt halogen light into my home socket and all's OK. Do you mean that a 575watt HMI light(like the elinchrom daylight 575 I'm looking at now) will pull more power than the halogen? And the voltage is stronger(dangerous)? I'm very ignorant about electrical stuff!

Yes. no. maybe.<P> Why don't you just ask Elinchrom instead of

having us just guess at the answers.?

http://www.elinchrom.com. while there check the info in the

elinchrom ringlight.

Tiago,

 

A 2000 Watt HMI light will draw about the same as a 2000 Watt Halogen light (a little more probably due to some loss in the ballast.

 

WHY A BALLAST IS REQUIRED:

 

The HMI light is more like an arc lamp. The result is that it will attempt to draw more power as it gets hotter, which in turn makes it hotter so it will want to draw more power. Well you get the idea that the more power it draws the more power it is capable of drawing. To fix that problem the have developed a "ballast" which limits the amount of power to the light to the correct amount. Without the ballast the light would burn up in a falsh. With the ballast the light will last a good 500 hours.

 

The ballast can also be quite heavy .. note that the Mole 4000 watt ballast is about 200 lbs (thats with the cart).

 

Others have suggested that you consider a serious flash setup. One other advantage of the flash units is the ability to adjust the power level. The HMI lights generally only have "off and on" for the controls (a bit limiting).

 

Ken

Thank you very much Ken and everyone. Your great help and advice have pointed me in the right direction. Sounds like I'll be getting that Elinchrom 575 secondhand for my portraits (an expensive way to avoid using flash! but I have my reasons...)

Any warnings before I call the bank manager? If not, thanks again for all the help. This forum is great (and full of good karma!). I hope to be able to contribute back with some experiences of my own in the near future.

Tiago,

 

No .. no other warnings .. except that you might also check for a spare bulb. My understanding is that the bulb only last 500 or so hours. I don't know if they die suddenly or reduce their output. I would guess that they either die suddenly or that the just will not start anymore.

 

Elinchrom is a pretty reliable manufacture, and the 575 is still on their web site so I suspect locating a spare bulb should be pretty easy (probably mail order).

 

Ken

Tiago,

 

It sounds like you've got plenty of good directions from the rest of the crowd. I was not trying to worry you, but I've filmed in a lot of older (and some new ones) buildings where the power was suspect. 2K plus is a lot of light on a single circuit, but an AMP is an AMP, and if you don�t have trouble with the Halogen instruments, the HMI gear should be fine as well. As for the water warning � well GFI is a good idea in general around a set with water. If you are indoors it is not likely to be a big issue, but when you go outside and it gets wet, things can get �interesting� when you have a lot if fixtures and a lot of AMPs.

 

One thing I will suggest again is renting some HMI units for a couple of days to see just how well they perform for you. I�m not sure where you are located, but there are a lot of film and television supply firms that provide name brand HMI gear (soft boxes and cables as well as the lights) on a daily rate. Any reputable firm will also offer you free advice and help with any safety questions you may have electrical or otherwise. Think about bulb screens for instance � molten glass is a real bummer in your eyes � yes that goes double for halogens as well. Of course with a fresnel it is a non-issue. Also, please invest in a good set of stands and weights for anything as costly as an HMI � You won�t regret it; good stands last forever. People really do bump into stands more than you might think and a few dollars in support can save thousands in repairs.

 

If you would like more HMI use information, I would suggest checking out back issues of American Cinematographer, and some film/grip web sites. A quick search should offer half a dozen alternatives. You will also find some suggestions on shutter speeds that will work with HMI and florescent fixtures. Of course still images will allow more shutter choices, but you might still find some of the reference�s helpful as you run your test shots.

 

I notice you are also interested in Florescent Daylight alternatives (in another posting) . I�d suggest checking out the Plume site www.plumeltd.com and looking at the white paper on daylight bulbs. You should also take a look at Lowel�s florescent offerings www.lowel.com � they could offer good fill with an HMI as key. You might also find some of the suggestions in Ross Lowel�s book Maters of Light and Depth of interest. He does have some good ideas about rigging safety and electrical hook ups as well as great lighting examples. You�re also going to want to get to know your local Rosco and Lee filter dealer. You are going to want high temperature light modifiers and they can be a lot cheaper by the roll. Again, check out local film and TV supply houses, but also local theater supply firms. They may be the same people in your town. I would guess you are working with subjects that are likely to be startled by flash equipment (animals, children, non- pro models, etc�). A lot of TV studios have switched to florescent for base and fill lighting, and it is cooler and more comfortable for a wider range of guest.

 

Continuous light is great. Nothing beats the �big guns� if you have the space and budget for them. Good luck - Cecil

Try Coollights.biz for some awesome hmi's. I shot with a 150 frezzy on the bw shots under 2008 on my myspace page -- myspace.com/gabescindian

 

The quality of light is excellent. I use profoto strobes but right now I am on a continuous light kick.

 

Oh the cost is a third of the ARRI's

 

Gabe