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Photon Management
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Old January 18th, 2007, 01:41 PM   #1
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Newbie light questions.

Hi all!

I'm going to shoot some muscians in a music studio. My guess is that it's going to be small and cramped and that they will bother a lot more with recording music than worrying about how the video will come out. Having that said they will expect that a beautiful result though..

Well, for inspiration I had a look at U2s "how to dismantle.." CD/DVD where the group plays in a very beautiful studio. Has anybody seen it?

If you haven't they use single Kinos on the mic stands in front of muscians as well as other shooting gear visible. The whole thing is very dramatic with low light and where black is really black.

1. Can you put a dimmer on a kinoflo without messing up it's light?
I was thinking of pairing some Kinos with some small HMIs.
2. Can you put a dimmer on HMIs?

HMIs are more powerful than other tungsten light, right? If the studio is around 30 m2 (ehh 323 squarefeet?) Would 4 single kinos and 4 500HMIs light up around 10 people? I was also thinking of putting some green and blue gels for effect.

I may have some (tungsten) light to light a background. Hence mixing daylight, HMIs and Kinos with a warm background.

It looks good in my mind.. but I have no idea if it would work.. I understand it it's difficult to get what I mean.. I'm kind of new and find it hard to explain.. but any help is welcome!

Thank you.
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Old January 18th, 2007, 02:42 PM   #2
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Are there windows in the studio - i.e. is there any daylight coming into the room? If not, then there's no reason to use HMI's... and you can save yourself a lot of cash and headache. HMI's are more efficient than tungsten lights, but that comparison is usually made between straight hmi's and CTB corrected tungstens, where the difference becomes huge. If you're shooting a 400 watt hmi, white balanced to daylight compared to a 400 watt tungsten white balance to tungsten, the difference will be slight.

Most HMI's can't restrike right away, so once it's on, it's on. As for dimming, yes, many HMI ballasts can dim internally - but if it doesn't have a dimmer on the ballast, DON'T ADD ONE!!! Also, most HMI ballasts buzz or hum... meaning that the ballasts should be in a separate room if the band is trying to record usable audio. (Note: they can easily record a scratch track, but if you're in the room shooting, you're probably making enough noise yourself to basically rule out using the recording for anything except reference).

It sounds like in your case, you probably won't even need hmi's so that buzzing shouldn't be a problem.

Many Kino units are dimmable, internally as well. Some are "power-line" dimmable. Before renting, make sure you know which you're getting, and unless you know for a FACT that it's powerline dimmable, don't add a dimmer to a kino that doesn't have one already.

Kino tubes come in many flavors, only one of which is the 5500K daylight tube. They also make 2900 or 3200k tubes which balance extremely well with conventional tungsten units. That way, at least you start with all the same color temp light - all tungsten 3200 (which should be what the studio lights are anyways). If you want to warm the light or cool it, each unit will be easily gelled, whether Kino or conventional tungsten. Also, Kino makes special effects tubes which are colored... may fit your needs.

Lighting has come a long way and ventured into some cool technologies - HMI, Fluorescent, L.E.D., etc... but the truth is that sometimes good ol' tungsten is your best bet. Kinos are fantastic units, and for what you describe, they will work perfectly on the mic stands. As for how many lights you'll need... what stop do you need to shoot at? Instead of going in and just flooding the space with lights, make a conscious decision beforehand what f/stop you want to shoot at, and take the time to look up the photometric data for the lights you intend to use. If you know the dimensions of the space, and the approximate locations of your mounting points (stands, autopoles, clamp mounts, etc) and your talent, you can essentially do the prelight on paper with sketches, data sheets and a calculator. Its a lot more nerdy and technical than showing up with a kit of lights and just blazing away.... but for something like this where you actually know all the variables, it lets you plan ahead for your power needs. Why rent 1K units when you only need 150's? Why use huge stands and mounts when you only need scissor clamps?

Which looks more professional: showing up with a grip truck and taking 6 hours to light a 15x20 room... juggling lights back and forth, running up and down ladders to scrim lights, trying to approximate an idea in your head. OR showing up with a carefully drawn diagram and couple cases of the exact units you'll need, putting them in exactly the spots you planned, and making minor tweaks to end up with the look you were going for from the beginning? Obviously, this isn't the reality of a lot of situations... but in your case it sounds like you have this luxury. Take advantage of it!
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Old January 18th, 2007, 03:59 PM   #3
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Thanks Jaron for your long reply! I've read it a couple of times already.
First of all I'm not at all scared of the "nerd-approach". (I'd say that the majority of us in here would classify as such anyway, hehe..)
I just don't know how to. I don't have a clue where to start.

I'm going to see the place on Monday, then I will know a lot more. I checked some pictures out on the net and that's where I found the size info. But I don't think there are any windows.

Are HMIs much more expensive to rent than regular tungstens? Otherwise I don't understand why you suggest to get tungsten and filter. As you pointed out there's the problem with HMIs changing temp when they are lit, but otherwise? Why is it better to go tungsten in your opinion?

I also agree with you to only get the light necessary. I'm not looking to impress anybody, just try to do as well as possible.
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Old January 18th, 2007, 04:09 PM   #4
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Oh yes, I forgot.

The f stop is important why exactly? From what I've picked up the lens peforms slightly better somewhere in the middle (F4??) and it will affect you depth of field a bit. Otherwise, does it matter?

Since I planned to shot daylight I'd use the 5600 filter.

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Old January 19th, 2007, 12:30 AM   #5
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First off, sorry if I was cryptic with the response about HMI's. Basically, HMI's are fantastic units, but their real use is to balance against daylight. If you have windows that will show in a shot, it's sometimes easier to use daylight sources indoors to stay all the same colow... the other option being gelling the whole window CTO.

As for advantages of one light over another... well it's murphy's law in many ways. HMI's, while extremely reliable, cost exponentially more than tungsten units. That trickles down to rental too - a 400 watt HMI runs about $5500 to buy, where an equivalent tungsten light is about $300 or less. More importantly, globes (lightbulbs) for HMI's are hundreds of dollars, where tungsten globes are generally less than $30. If something breaks on a tungsten light, there's really not a whole lot to fix - a wire could be torn or a lamp could be blown. HMI's have a lot more circuitry, and generally aren't field repairable (unless you're really good with electronics). All-in-all, its FAR less expensive to use tungsten than HMI.

Another cool thing about using tungsten is that you can utilize non-pro lights mixed in. Need a quick accent light? Use a standard household fixture. Need some sparkle on a background? Poke white christmas lights though - they'll appear balanced perfectly. Feel like mixing in a flashlight? No problem. Basically, tungsten just gives you more options. There are few true daylight sources available, but there are essentially unlimited tungsten sources... If you're indoors, with no daylight reference, why limit your options by shooting daylight? A video camera white balanced to daylight and using daylight sources will read on screen exactly the same as if it were white balanced to 3200 with tungsten sources.

As for playing the numbers game, Arri's website has a fantastic calculator, just go to photometric calculator. On the bottom, go to camera expert. Most DV/HDV cams are roughly 320 film exposure index (good rough estimate). Shutter angle - For 24P (24 frames/second framerate), shutter speed should be 1/48th or 1/50th of a second, corresponding to 180 or 177 ish degrees respectively. Pick out the wattage based on the light you're thinking of using (300 juniors are a good start), and pick a distance. If you hit calculate, it'll tell you what stop you'll get. (Note: most lights of similar design have similar photometric performance. So, even if the brand of fresnel or open-face light is different than Arri, the corresponding light of theirs should be pretty darn close... close enough for planning purposes at least).

As for the importance of stop - picking it ahead of time gives you some control of your depth of field. In general with small chip dv cams, wider is better. Same with most broadcast cameras (2/3" chip)... helps to lessen the "video" look. But picking a base stop is important for the reason that it allows you to actually calculate your lighting needs ahead of time. Obviously, when you get to set and have everything laid out, it may vary a bit.... but you should be awfully close.

Anyways, hope that helps clear things up a bit. Good luck with the shoot!
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