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Preplanning a large practicle instalation


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#1 Michael Collier

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Posted 20 November 2007 - 10:26 PM

I am working on prep of a new short, and I have come to a stumping point when planning for the last scene.

The location is a large indoor bar, with no windows or large light sources. Walls are darker floor is very dark. I want to light the set with a lot of practicles to make the two day action finale shoot go smoothly. To this extent I have decided to build practicle base level of exposure into the set using christmasstree lights, spaced 6" apart on each string and maybe 1-2 ft between each string lengthwise. I want to get to about 3-4 stops under key consistently throughout the room. I might have one or two 2-4 hour nights to pre-rig the set with the gaffer and maybe a grip.

The problem I have is I want to know what that spacing should be between strings to put enough light into the room. I want to test the lights before hand, but I can't think of a good accurate means to do this. I don't want to overbuy on lights, I don't want to rig half and decide its too much or too little and start over, I don't want to over-rig and then end up removing half the bulbs from their sockets.

to add complications to the matter, I can't scrim or gell in anyway, and since they are x-mass tree lights, they are already a bit on the warm side, so that makes dimming them difficult, unless I start to add a complimentary CTO to ALL the other lights to ballance (including other practicle, difficult to gel lamps).

so....what is the best way to test this? I know I can't be the only one to have run into a problem like this? Should I rig up a test section two or four times as wide as the distance to floor, meter in the center and assume the inverse square will minimize the effect of lights that would be farther than that? Thats the best I can think of and I have been thinking on it all day, I know there must be a better solution.
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#2 Michael Nash

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Posted 20 November 2007 - 11:38 PM

The obvious thing is to build a rig and test it in a dark room, metering it at distance similar to the way it will be rigged on location.

How are you going to rig these lights at the location? It seems an easy way would be to string them up on empty 4x4' frames, then somehow mount or hang those frames from the location ceiling on the day. Maybe back the "up" side with white showcard as a reflector.

If it's just for a low ambience, then why should it matter that the color temperature is warm, or matches the practicals? It might end up looking kind of interesting.

I wonder though, if all you're after is a low ambience, how hard would it really be to tape some white showcard to the ceiling and bounce/skip a few clip-on worklights across it? Or maybe tape up a few 4' fluorescent tubes. Or small Chinese lanterns.
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#3 Michael Collier

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Posted 21 November 2007 - 09:58 PM

The frame idea, showcard and floros wouldn't work, since the idea here is to build base level exposure in a manner that can be shot in frame and encompase the entire ceiling. There will be several steadycam shots, some 360 steady cams, and I wanted to make it easy to light for, given the dark contrasty look I am after. I need a general low level of fill light coming from the all over the ceiling all at once. We are shooting HD, so I definatley don't want any part of the frame going completely into black, though I do want to get close. With the location being so dark in art direction, I need the base to cover me.

Also since there is the big show finale fight/gun sequence, I need it to be quick and easy to light shot to shot, since we have one night of dialouge and one night of fight, and lots to do in that time. I want to see the lights, but have them be just small unobtrusive. If theres a blanket of small lights, it will define the ceiling and fit the sky/star motif the director wants.

Color tempature of the base is extremely important, since it is the finale and we are developing an arch in the lighting of the various bar scenes throughout the short, and by this point tone with color highlights is the name of the game. AFter all the bar at the end is called 'Blues Place'. warm light will be introduced, but all shadows must be nutral or shifted slightly to blue (accomplished through whitebalance/post grade) Normaly I like warm shadows, but for this scene it definatley would not work. I won't have the base and keys matched in terms of color temp, but I would like to get as close as possible to white from the base. If I grossly mis-estimate and end up dimming them to 20% then I must adjust all the keys, which adds more time and complication (also theres the nagging fact that the producers won't like buying a bunch of extra dimmers if I make them buy too many light strings.)

The only problem with testing in a dark room is the room I am working in is probably 25ftx50ft. I don't have access to a room that big to test with. I am wondering if there is an accurate scale test I can do and rely on? Any ideas? I am desperate for some insight. I can do a scale test, but don't know if I can rely on that, if my assumptions are wrong.
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#4 Michael Nash

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Posted 22 November 2007 - 05:13 AM

I think you're probably going to need a LOT of christmas lights, densely packed to light that large an area (even 3-4 stops below key). Take a look at the walls of lights in that early scene in Eyes Wide Shut as a reference. You can still test a 4x4 or 6x6 "patch" of lights in a dark room (either with a light meter or the camera) and see if you're even getting close. You know that a larger are will give you a little more stop (depending on ceiling height), and you might be able to string them so that you can unplug every other strand if it ends up too bright.

I'm not sure what avoiding black has to do with shooting in HD though, unless you're talking about the noise you get with the HVX200 in low light. That noise will still be there with a frame full of detail that's dark but not pure black anyway. If that's the whole reason for keeping a very low base ambience, I don't think it's going to help you much.

If you want bluer Christmas lights you might take a look at the white LED variety. They'll cost a bit more though.
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#5 Michael Collier

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Posted 22 November 2007 - 02:00 PM

Thanks Michael. I will try the 6x6 out and see how well it works. I figured I would need a ton of lights, which rules out LEDs for sure, given our budget for things like these. If you saw the location and the lighting plan you'd understand why a good base is so important.

In HD I try to avoid hitting the black clip, since it does make noise and stepping more apparent (though your right, more light doesn't fix this, it just hides it) And unlike film which can really reach into those blacks, HD just doesn't look right when it hits clip, and this scene will have SO many large areas that are reaching down to that level, that a nice general base will really help me move quickly without worrying about my shadow detail being lost completely. I can always crush the blacks a little in post grade if its too much (further supressing shadow noise) but I don't want to bring it up.

For now I am planning the HVX-200, with neg-gain to bring us somewhere in the 200asa rang (thats whats dialed into my meter for testing right now) Its possible we might go with a redrock adaptor, though I am warry of that since we have a couple of very large night scenes, and all I can get is two 2.5k HMIs (oddly enough, they are the most powerful lights avalible in this state) shooting 100asa would be difficult to get the scope we want on those shots. We also might shoot a JVC HD-250. I am still trying to lock down camera for the budget we have. Makes planning lights difficult when your not sure exactly what your going to rate the camera.

happy thanksgiving everybody!
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#6 Michael Nash

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Posted 22 November 2007 - 02:56 PM

In HD I try to avoid hitting the black clip, since it does make noise and stepping more apparent (though your right, more light doesn't fix this, it just hides it) And unlike film which can really reach into those blacks, HD just doesn't look right when it hits clip, and this scene will have SO many large areas that are reaching down to that level, that a nice general base will really help me move quickly without worrying about my shadow detail being lost completely. I can always crush the blacks a little in post grade if its too much (further supressing shadow noise) but I don't want to bring it up.


That sounds like a function of whatever gamma setup you're using, and not HD in general. Most video cameras actually have an incredible amount of information down in the "toe." For example I was testing a Panasonic HDX900 camera yesterday to try to map its response curve in the Filmlike 2 setting, and found that (like most video/digital cameras) the further I went underexposed beyond 3.5 stops, the less it pushed the exposure down, rolling off the shadows quite gracefully. It required at least 5 stops of underexposure for a gray card to hit 0 IRE. The only time I've seen blacks clip unnaturally in video is when either the pedestal (master black) was crushed below zero, the black stretch (black gamma) was raised all the way up, or both.

Some of what you're describing also sounds like the crappy black reproduction of many LCD monitors. Try testing your camera against different properly set-up field monitors, especially a CRT. Sometimes having the backlight too bright on an LCD monitor can make the rolloff into black appear artificially bright and unnatural (revealing more noise).

The HVX200 shouldn't clip the blacks in CineV or CineD gamma with the pedestal set to zero, although it IS a noisy camera in those settings. And what I was trying to say is more light in the shadows doesn't hide the noise -- the noise is actually MOST visible in murky shadows between 0-10 IRE. If you really want to avoid noise, you're better off crushing shadows into solid black and keeping everything else above 10 IRE -- which of course is impossible in the kind of low-key scene you're describing.

If you simply don't care for the look of pure black in your image then fine, there's nothing wrong with that. Just bear in mind that increasing contrast and lowering black levels in post can actually make noise and compression artifacts even MORE visible.
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