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Flourescent help


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#1 Mackay Valentine

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Posted 10 December 2007 - 01:23 PM

Hi All

I'm preparing to shoot a 35mm short in a couple of months, and I'm just about to begin testing. The majority of the film takes place in a number of small pharmacies, all of which are locations, and like all pharmacies they all are lit with rows of flourescent fixtures. They also all seem to vary in color temperature, with some of the bulbs warmer or cooler than others. Now ultimatley, I plan for the look of the film to progess from a warm-soft white to an unattractive contrasty green. I know there are many ways to go about controlling color and contrast, and I dont know where to begin with this dilemna. Should I correct the color of my own lights, or the house flourescents? Also, do I have to worry about flickering? Whats the best way to go about doing this on a budget? Anyones advice would be greatly appreciated.

Thanks
Mackay
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#2 Michael Nash

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Posted 10 December 2007 - 04:58 PM

The easiest thing to do is to match your movie lights to the color of the existing fluorescents at the locations. If you're using Kinoflos you can put spare tubes from the location in the unit, or buy new ones that match what's in the building. For your tungsten lights just carry various densities of CTB and PlusGreen to match the fluorescents. Use a color meter or a digital still camera to ensure the right color match. Even when there are mixed tubes at a location, there is usually one predominant color balance that you can match to. You can color correct the film image in camera with filters, or in post.

Fluorsecent lights follow the same flicker rules as HMI's, since the ballasts cycle with the frequency of the power supply. You won't have any flicker at 24fps crystal with a 180 degree shutter.
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#3 John Sprung

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Posted 10 December 2007 - 06:17 PM

These being small pharmacies, do you have the option to keep the actual flourescents out of all your shots? Do you have big windows and daylight, too?

Another approach would be to minusgreen sleeve the flourescents, or turn them all off. Foam core and bounce from the ceiling to get soft light coming from where they could reasonably have been. It's a lot more work, but gives you more control. You can put the foam core where you want the light. Plusgreen can also be scary for unsophisticated suits and producers. It looks very weird in real life.




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#4 Phil Bradshaw

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Posted 10 December 2007 - 07:29 PM

If you have the option, I would meticulously scout the locations you will be shooting in. When you are dealing with several flourescent fixtures, you're bound to have a few ballasts that are old or starting to burn out. This will create pulsing in the lamps and a color temperature shift (which gets worse as the ballast starts to decay). Find out the ballast specs and have production purchase a few extra.

As far as bulbs, Philips makes Colortone C50 bulbs that are rated at 5500k, and Alto bulbs rated at 3500k and 3000k.

Also, test the breakers that the fixtures are on so that you will have flexibility when changing bulbs quickly without damaging the ballast. I always avoid "hot-swapping" flourescent bulbs whenever possible because the pins tend to arc against the metal in older fixtures, which can severely damage the ballast and cause injury.
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#5 Andrew Jackson

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Posted 13 December 2007 - 02:34 PM

If you have the option, I would meticulously scout the locations you will be shooting in. When you are dealing with several flourescent fixtures, you're bound to have a few ballasts that are old or starting to burn out. This will create pulsing in the lamps and a color temperature shift (which gets worse as the ballast starts to decay). Find out the ballast specs and have production purchase a few extra.

As far as bulbs, Philips makes Colortone C50 bulbs that are rated at 5500k, and Alto bulbs rated at 3500k and 3000k.

Also, test the breakers that the fixtures are on so that you will have flexibility when changing bulbs quickly without damaging the ballast. I always avoid "hot-swapping" flourescent bulbs whenever possible because the pins tend to arc against the metal in older fixtures, which can severely damage the ballast and cause injury.



My words of wisdom: be careful. I did a lot of research before filming under fluorescent lights for my senior thesis. I looked up numbers on the bulbs, made sure they were all the same, and called the facility operations for the building, in which case they told me all the bulbs were less than a year old, and all were 3500k. I bought some compact fluorescent bulbs, rated for 3500K, and put them in fixtures to use as fill lights and such (and would balance the color in telecine). I did some reading about flicker problems in several books and forums, all said I would be fine....but my footage came back with some horrible flicker (some shots/angles worse than others). I didn't know why, but what you are saying Phil, with the the ballast units being old, makes sense. I was so confused the past day trying to look up what could have gone wrong...

If you're serious about this piece, I definitely wouldn't rely on the "practical" lights that are already there...use your own units if you can.
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#6 Phil Bradshaw

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Posted 13 December 2007 - 03:02 PM

My words of wisdom: be careful. I did a lot of research before filming under fluorescent lights for my senior thesis. I looked up numbers on the bulbs, made sure they were all the same, and called the facility operations for the building, in which case they told me all the bulbs were less than a year old, and all were 3500k. I bought some compact fluorescent bulbs, rated for 3500K, and put them in fixtures to use as fill lights and such (and would balance the color in telecine). I did some reading about flicker problems in several books and forums, all said I would be fine....but my footage came back with some horrible flicker (some shots/angles worse than others). I didn't know why, but what you are saying Phil, with the the ballast units being old, makes sense. I was so confused the past day trying to look up what could have gone wrong...

If you're serious about this piece, I definitely wouldn't rely on the "practical" lights that are already there...use your own units if you can.


Old ballasts also cause annoying sound issues and tend to overheat the fixture. Using available location fixtures can also open a can of worms for troubleshooting problems. The best thing is to do a camera test during pre-production with several varieties of bulbs and fixtures. This way you can place your bulk orders accordingly, and you know exactly what you're getting visually.
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#7 Jess Haas

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Posted 13 December 2007 - 03:28 PM

If using house bulbs in kino 4ft fixtures start with the ballast in 2ft mode. 4ft mode is for high output bulbs so it will overdrive regular bulbs causing a color shift and more of a green spike. 2ft mode will give you standard output for a 4ft bulb.

Andrew, did the flicker appear to be coming from just a fixture or two or was everything flickering? If the later was the case I would guess that either your camera wasn't running at a solid 24fps or your shutter angle was too small.

~Jess
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#8 John Sprung

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Posted 13 December 2007 - 04:02 PM

I did some reading about flicker problems in several books and forums, all said I would be fine....but my footage came back with some horrible flicker (some shots/angles worse than others).

There are two different kinds of flourescent flicker:

1. The "normal" 100 or 120 light pulses per second at twice the AC power frequency, 50 or 60 Hz. This can cause visible beat frequencies if you get the frame rate and/or shutter angle wrong.

2. The slower random instability of output from old bulbs or old ballasts, sometimes slow enough to see with your eyes.

If the camera isn't really running at exactly the right speed, you'll also have a big sync sound issue. If you have a 180 degree mirror shutter, you can check by running the camera without film. If you see beat frequency flicker in the finder, you'll have to solve the problem before you shoot.




-- J.S.
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#9 Hal Smith

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Posted 13 December 2007 - 04:32 PM

Not the cheapest piece of equipment around but there is a flicker meter that works.

Flicker Meter
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#10 Andrew Jackson

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Posted 14 December 2007 - 03:32 PM

I was using a crystal sync camera running at 24 frames per second with a 180 degree shutter. The sync light never came on (except at the very beginning of course), so I assumed that it stayed at a constant 24, although the equipment we were using is old. I didn't hear any noise coming from the fluorescent lights.

We have a few shots from different angles. I had mentioned we used a 3500k compact fluorescent light as a fill, as the overheads were all rated for 3500k. We only used one of the compact bulbs though and it was focused on the actors, so the flicker couldn't have come from that one. The most visible flicker can be seen by staring at the walls (although you can see it on the actors, it's just harder to catch with them moving). I believe we do have enough coverage to edit around and not make the problem apparent.

Although I've shot 3 films now, I still feel like I know about 5% of what there is to know....so bare with me here. A buddy of mine shot in the same location a year ago, in black and white, on 16mm non-sync camera (although, he also shot at 24 fps and 180 degree shutter). He claimed he didn't get any flicker. So, my thoughts
1) either something about the lights were different then
2) black and white doesn't show flicker as well
3) what is actually "flickering" is the color temp, and that's why it wasn't really seen on black and white (mine is shot in color)
4) he just didn't notice the flicker (he had a couple of fast cuts and lots of movement in the frame).
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#11 Andrew Jackson

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Posted 14 December 2007 - 03:39 PM

Blah, didn't make the edit on time:

Thanks for trying to help me solve this, guys. Umm...I didn't see flicker through the viewfinder, although I was mainly watching the actors performances when I was running the camera. And from the 4 shots -> 3 were in the same room(verse, reverse, master) and then another was shooting from outside the room as our actress walked past the camera and into the room where the dialogue takes place. Hard to tell if it's coming from a certain light, but in our master it seems worse than in the verse, reverse shot. Our master is a side/2-shot, and the others are over-the-shoulders, so we actually do see different parts of the walls.
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