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Which HMI do I need


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#1 Adam Wallensten

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Posted 27 February 2007 - 06:19 AM

Hi!

I'm shooting a musicvideo this weekend and one of the scenes is staged on a beach where the band is going to perform a dance. We will use the water and sky as the background and light them from the front with probably just one HMI with some diffusion. My question is, how powerful a HMI will I need. Is a 2K going to be enough to light their fronts and not have the background burn out? I'm supposing it will be sufficient in the closeups but how about the bigger framings? By the way, I'm shooting on a Panasonic DVX-100.

I would appreciate your thoughts on this, and please ask if you need more info to answer my question.

Thanks

Adam Wallensten
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#2 Matt Sandstrom

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Posted 27 February 2007 - 10:42 AM

it will be enough for closeups but if this is in broad daylight not for the entire band. i guess most people would suggest an 18k for such situations but i'd get a 4k. those still run off a small genny. since it's a music video it doesn't have to look right so you can even spot it, use very little diffusion and get some cool vignetting. i only shoot low budget music videos so i've no idea how to do it properly anyway. i leave that to a real dp when i direct fiction. ;-)

/matt
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#3 Thomas Burns

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Posted 27 February 2007 - 07:56 PM

Adam,

The big question here is what the weather will be like, as a sunny day at the beach could require substantially more light than the overcast alternative. I would feel uncomfortable competing with a sunny beach on video with anything less than a 6K PAR, and even that could be dicey. You might try some grip lighting (a 12 x 12 bounce), though this option has its own set of variables (wind, changing sun, intermittant cloudcover, etc.). All of the day exteriors I've worked on at beaches have involved multiple 18Ks, but I understand that this approach may not be an option. A 2500 HMI will not be sufficient. You will do well to make sure whatever head you choose is a PAR and not a fresnel. Lots of putt-putt generators won't support a 4K, so be sure you inquire (and test!) at the rental house first.

Beach shoots can be . . . challenging. Good luck, and let us know how it goes.

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#4 chris kempinski

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Posted 27 February 2007 - 09:09 PM

here is my opinion,
I agree with Thomas about a 2500 not being enough.
As long as you get a powergems electronic ballast, you can run a 4K at 208V (sometimes the europeans do have it right). You do need the correct addapter for the gennie, 4 pin to joy, or a transformer to drop you from208V back to 120V but it is wise to check with the rental house and test it all before you show up on the day.

Secondly,
If it turns out to be a sunny day..... use a 20X20 silk or full grid to heavily diffuse and block the sun, then, get about three mirror boards and bank that sun stright into a 12X12 or 8X8 diffusion. it's almost as good as an 18K and the color temp stays the same as well. the problem arises, if the sun isn't there, or the clowds roll in (this is when my idea turns to junk) you don't have the 4 18K's to keep shooting the look you've just established.

good luck
post your results when it's said and done so we know what you ended up doing.
Cheers
Chris

Edited by chris kempinski, 27 February 2007 - 09:11 PM.

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#5 James Brown

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Posted 05 March 2007 - 05:54 AM

Hi,

By the sounds of it you dont have a huge budget. If the sun is out one of the options you have is a 12x12 silver (maybe soften it with the white) bounce. Otherwise you would need at least a 4k or 6k Par as discussed earlier. That means, generator, at least two electrics ect..... And for the wide shots, obviously depending on how wide your going a 4k isnt going to give you a lot of kick. My bet is bounce if it's sunny. Big HMI shot through a frame for some spread if it's overcast.

Cheers, James.
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#6 Adam Wallensten

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Posted 05 March 2007 - 09:16 AM

Thank you for your advices!

The beach-shoot was yesterday and things didn't turn out quite as we planned them to. Since the budget was super tight the only lightin we could afford and run of the rented 3.5 generator was a 2.5 kW HMI. We also brought some mirror-reflectors, silks, etc. We hoped to use the sun as the main light and use the HMI for fill.

When we arrived at the beach there was the most beautiful sunrise in which we got some great shots of the band walking as silouetes towards the beach. Then when we were setting up for the first performance shot the HMI wouldn't work. When we turned it on it lit up faintly for about 5 seconds and then it swiched off. For some reason the generator couldn't run it. The rental place couldn't help us over the phone and since we were out on the countryside with a limited time to shoot, we just had to ditch our artificial light.

After some re-planning we were ready to shoot using only the sun with some reflectors. After a couple of shots a the sky turned to overcast and everything turned gray... The reflectors were not of great use and the rest of the day we had to shoot in this very naturalistic condition ;) (at least it stayed gray). Not exactly the look we were hoping for....

Well well, we all did our best and hopefully something good will come out of it. Luckily the whole concept of the video was a kind of lo-fi documentary style...

I appreciate all of your advice though...

Adam
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#7 robert duke

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Posted 05 March 2007 - 09:34 AM

Don't forget the grip world can assist you as well with 4x4 mirrors and shiny boards. If you luck out and get a sunny day the sun can give you a no power 18k. also 12x12 silver lame or a rag that I only know of as a microwave ( it is like a chrome/silver grifflyn) I think it is via matthews. beach days for me have always been grip days.
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#8 JD Hartman

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Posted 05 March 2007 - 10:26 AM

When we arrived at the beach there was the most beautiful sunrise in which we got some great shots of the band walking as silouetes towards the beach. Then when we were setting up for the first performance shot the HMI wouldn't work. When we turned it on it lit up faintly for about 5 seconds and then it swiched off. For some reason the generator couldn't run it. The rental place couldn't help us over the phone and since we were out on the countryside with a limited time to shoot, we just had to ditch our artificial light.

Well well, we all did our best and hopefully something good will come out of it. Luckily the whole concept of the video was a kind of lo-fi documentary style...

I appreciate all of your advice though...

Adam


The problem is the size of the generator. A 3.5kw generator supplies 3500 watts peak output for a brief time before the alternator overheats. You needed to choose the generator by its continuous load rating, which may have been 1000 watts less. Both ratings, surge watts/continuous watts, should have been on a plate somewhere on the generator.
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#9 Adam Wallensten

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Posted 05 March 2007 - 01:28 PM

The problem is the size of the generator. A 3.5kw generator supplies 3500 watts peak output for a brief time before the alternator overheats. You needed to choose the generator by its continuous load rating, which may have been 1000 watts less. Both ratings, surge watts/continuous watts, should have been on a plate somewhere on the generator.



It was the rental-place that we also rented the HMI from that provided us with the generator. They told me that it had been used many times before and that it had always had worked. So there shouldn't have been any problem with the two working together.
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#10 Jonathan Bowerbank

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Posted 05 March 2007 - 04:29 PM

Don't forget the grip world can assist you as well with 4x4 mirrors and shiny boards...


I would agree that reflectors and bounce boards are probably your best option, especially if it's a sunny day, even if it isn't, reflectors can still be pretty effective. You'll already be getting a lot of bounce from the sand itself (unless it's volcanic...but I don't know the Danish beaches), so as long as it's a daytime shoot, I wouldn't worry about having to trudge a bunch of HMI's out to the beach.

update: oh, should have read further on to know that the shoot already happened...well, this one's for future forum readers I guess!

When we arrived at the beach there was the most beautiful sunrise in which we got some great shots of the band walking as silouetes towards the beach. Then when we were setting up for the first performance shot...


I'm sure you probably learned a big lesson in time management as well...perhaps I'm just misjudging, but someone should probably have been setting up the performance set as you were getting the silhouetted shots.

Hope it turns out well though! Be sure to post some footage if you get the chance :)

Edited by Jonathan Bowerbank, 05 March 2007 - 04:25 PM.

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#11 Hans Engstrom

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Posted 21 March 2007 - 08:45 PM

It was the rental-place that we also rented the HMI from that provided us with the generator. They told me that it had been used many times before and that it had always had worked. So there shouldn't have been any problem with the two working together.


That´s the reason why I allways test everything before driving away with any equipment from the rentalhouse. Sometimes they can be a little grumpy and say something like "don´t you trust us?". I allways answer that it´s not because I don´trust them but because I´m getting paid to do it and if anything doesn´t work I´m the one that have to explain to the producer why we can´t shoot that day and after that I promise you that he will not hire me again. Testing the equipment at the rentalhouse also gives you a quick update on the equipment if it´s been a while since you worked with it.
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#12 David Mullen ASC

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Posted 21 March 2007 - 09:18 PM

I find that it's hard to use any HMI's bigger than 1200w on these put-put Honda-type generators even if the amp rating seems to allow it -- maybe it's the start-up charge of the HMI or something... on my fourth feature in 1994 I had a similar problem doing nighttime pick-up shots on a snowy mountaintop in Big Bear. The 2.5K HMI wouldn't run on the 90 amp genny. Luckily all the that white reflective snow -- plus some fortunate fog -- meant than even the underexposed light from a 1.2K HMI looked like I was using a 12K HMI on a condor!
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#13 Michael Campanella

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Posted 24 March 2007 - 09:24 AM

It was the rental-place that we also rented the HMI from that provided us with the generator. They told me that it had been used many times before and that it had always had worked. So there shouldn't have been any problem with the two working together.


I've had this happened to me twice out on locations. The first time, I took it as a learning experience. The second time I warned the photographer of this problem, and he decided to neglect my advice because the rental house told him it wasn't a problem. I feel your pain.

Edited by Michael Campanella, 24 March 2007 - 09:28 AM.

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#14 Matt Sandstrom

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Posted 26 March 2007 - 12:33 PM

silly questions perhaps but did you know how to operate the genny? on automatic they often won't strike a big hmi, while on max they will, and then there's choke and throttle, and sometimes you have to open the lid to the fuel tank to let the gasoline flow. and so on. it's not just amps but combustion and mechanics too.

/matt
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#15 Alessandro Machi

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Posted 26 March 2007 - 02:38 PM

The few occassions I have shot at the beach I always bring some type of spider pod or ladder so that I can elevate and shoot slightly downward. The advantage is I get to expand the depth of the sand over more of the background frame. In your situation more elevation would have allowed you to use the colorful water as your background rather than an overbright sky.

Matt may be on to something in regards to the generator and it's ability to handle a sudden temporary surge in power requirements when you first attempt to turn on the HMI. Additionally, I was told that once outside temperatures go over 80-90 degrees farenheit the actual efficiency of the generator begins to decrease. At a hundred degrees farenheit you might experience a 10-20% drop in overall generator power output capacity. Early in the morning that probably wasn't an issue for you but later in the day it could have become a factor.

Just for curiosity's sake and to learn, have the generator rental house show you what you probably did wrong by having them turn on the actual HMI light that you rented. If they can't turn it on with their own generator, then they owe you a refund and perhaps a free rental as well (as long as the free rental doesn't involve any extra manpower on their part such as delivery or pick-up.)
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