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HMI's at night


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#1 Alexander Disenhof

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Posted 01 December 2007 - 08:58 PM

I am a student at Emerson College in Boston, and I was walking down the street tonight and saw the new film "The Lonely Maiden" (I think thats what its called) starring Christopher Walken and Morgan Freeman shooting. Naturally, I was interested in the light units they were using, and so I talked to the 3rd electrician. I asked about a light about 200 yards away, which looked something like a 12K HMI or something of the sort. Instead, he told me it was a tungston unit, and said that one should not use HMI's at night, because they are only for simulating daylight. To make a long story short, I would have thought that using HMI's at night could be a good way to get the blue light usually associated with the moon. Am I wrong here? Is it just a no-no to use HMI's at night, even for a blue rimlight or something? Or, if they are used at night, what are some of their common uses?
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#2 Michael Nash

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Posted 01 December 2007 - 09:49 PM

There's no right or wrong here, and that electrician's statement was pretty broad. Not necessarily wrong, just broad.

People use HMI's at night all the time, specifically for the blue-tint you mentioned. But if you want some color other than blue, it doesn't always make sense to start from a color temp of 5600 and add gels to that. For example, if you're trying to match or fill-in sodium vapor street lights you'd usually want to start with tungsten light and gel that, rather than heavily gel a blue source to get orange. And many people use a color temperature of about 4300 for moonlight, which can be achieved by 1/2 CTO on an HMI or 1/2 CTB on tungsten. It just depends on the units you prefer to use, power, and so on.

As for uses of HMI's at night, a horror film I gaffed this summer used "moonlight" of 4300K + White Flame Green. We lit up a vineyard with two 12K HMI's in a condor gelled with 1/2 CTO and WFG. To get the same light level by gelling tungsten would have required more large tungsten units and more power, and probably separate condors to mount the extra lights. This would have cost us major time and cabling between setups.
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#3 David Mullen ASC

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Posted 01 December 2007 - 10:38 PM

Another reason why HMI's get used for blue moonlight for large areas of night is that you're renting these big lights anyway for your day scenes, so you might as well use them for your night work. As opposed to some big Dinos or other powerful tungsten units, like 20K's, which you may not be using for interiors on location shoots, so you'd be renting them just for these night scenes.
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#4 Alexander Disenhof

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Posted 01 December 2007 - 11:22 PM

Michael and David, thank you very much for your answers to my question! Also, I want to thank you for taking the time and answering so many people's questions on this forum, I have already learned so much from just reading your posts every day! Being a student, I have not had the opportunity to work with huge budgets, and so David, your info on renting certain lights to consolidate resources and therefore save money for the production is something that I will definately keep in mind as the films I work on get bigger!

Thanks again.
Alex
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#5 timHealy

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Posted 02 December 2007 - 07:38 PM

I agree with Michael's response about using HMI's at night that there is no right or wrong. but one issue I have with using HMI's at night is that they are more complicated than tungsten units. So generally speaking, HMI's are prone to more problems than a tungsten unit. So using tungsten at night may be a little easier. I am sure someone will respond that they use HMI's all the time at night and have never had a problem. Perhaps they have not had a problem yet. But when one has to wait for the electricians to trouble shoot a large HMI rigged in a lift with the AD looking at their watch and then you over and over. But unless one has a specific reason to use an HMI, I would stick to tungsten.

Best

Tim
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