Designing with HMI fixtures

[SalvatoreDelorean]

My college just got its hands on a bunch of HMI fixtures (mainly ARRI Studio Fresnels and Selecon Pacifics), and I was thinking about using a bunch of them for an upcoming production of The 39 Steps I'm lighting in a few months. I don't know much about HMIs, but the director really wants to emulate the look of film noir and old cinema (The 39 Steps is adapted from a Hitchcock movie), so I figured using the Arris, which are film/studio lights, would make sense to some degree. However, I don't have much knowledge of HMI sources/Arc lights, and I'm curious how the design process is different when using them in place or alongside tungsten fixtures. I've heard them described as complex, and drastically different than working with tungstens, but I'm a little confused as to how that's the case. I know they produce a cooler, whiter color temperature that's closer to daylight, I know they're a lot brighter and that they use mechanical dimming, but I'm curious how that translates into making design decisions when coming up with a plot or cueing a show. Why would a designer choose to use HMIs over tungstens? Why are they used in opera so much?

 

[rochem]

The biggest use I've seen for HMIs is when you want a really strong, singular idea. They can fit into the same category as Beam Projectors and 5K Fresnels. They're excellent for making strong, bold statements, and they cut through everything else.

You do need to consider a few things when specing them. For one, they don't dim, so you'll need to use a mechanical douser to turn them on and off - something like Wybron, Inc. - LF Eclipse IT Shutter is fairly standard. Depending on the fixture, you'll probably also need a hot 60A circuit to power the fixture - NOT a 60A dimmer switched at the rack. You also need to keep in mind that the color rendering is going to be much different than with a tungsten fixture. It's not uncommon to put a color scroller on these, but you need to account for the fact that gel colors, especially saturated colors, will have very unexpected effects on the light. If you're going to gel it without a color scroller, know that they will burn through deep colors in a matter of seconds, not minutes - I've had to do some pretty crazy "diapering", taping four full sheets of gel together at the corners and blacktacking the gel onto the front of the barn doors just to make the color last. Also, because the light quality is different, you generally won't use these for face light. Every time I've had a designer use them, it was as a diagonal back or a medium side - with diagonal backs being by far the most prevalent. Really the best way to use them is to play with them. We rented a couple of HMI 4Ks from PRG for a show last year, and it was the designer's first time working with HMIs, but he loved the effect and it worked really well for the show.

If you saw the Broadway revival of Ragtime three years ago, Don Holder made use of four HMI Fresnels as diagonal backlight with scrollers on them. From what I saw, the HMIs allowed him to cool off the scene and give it a more sterile look, but he also used them for deep saturated colors.

A stage photo - the HMIs are the larger lavender sources visible at the top of the image:


Plot:

 

[JD]

Another consideration is start-up and re-strike times. A dip in the power source (even from the electric company) may drop them and they may be off for several minutes. Once they strike, there is a ramp-up time needed before they attain their working output and color temperature. As was said above, any dimming / dousing needs to be mechanical in nature. Also, light bleed from the fixture may be a problem unless precautions are taken.

 

[jglodeklights]

First, I would suggest watching several films in the style the director is looking for and possibly going so far as to break one or two of them into "cue lists" that describe the scene and how the lighting is creating mood and how it appears to be created. I think you'll find that just because the Arri's are "film/studio" fixtures, doesn't mean that they will necessarily work to create the style of lighting you wish to have once you hang them in your theater.

As Michael and John stated, they don't dim and have a completely different color temperature and balance in comparison to tungsten. It is the lack of dimming that will be most important to consider when cueing the show.