Lighting Room w/ Mixed Light Sources
 

Here's the shooting scenario with some challenging lighting:

Institutional, double-wide trailer with one open area - half filled with seating for group meetings. Small, uncovered windows set fairly high along both the long north & south walls. Will be recording interviews of individuals here and, later, a group meeting for a documentary-style promotional.

The north windows are at the back of the room & won't be in the shots, but the south windows will be directly behind the leaders during the meeting. All recording will be during daylight hours. Overhead lighting is fluorescent. My tungsten-halogen light kit includes a 750-watt broad throw and both 500- & 250-watt spot lights. I would like to place diffusion material on the outside of the south windows - but would appreciate budget-conscious material suggestions. How would you work with the windows, varied light temps, overall light levels for both the interviews and, especially, the group meeting?

The situation you describe is challenging.

First, try to avoid mixed temperatures on faces. If you have access to the location, try to figure out what these fluorescent bulbs are. "Cool white" is generally closer to daylight, "warm white" closer to tungsten. If they are cool white, can't be changed out, and must be on during the shoot then use some 1/2 or 3/4 CTB gel on your tungsten lamps to bring them closer to the fluorescents. This isn't an expensive product.

Problem number 2 - relative intensity of the south windows. You're probably going to need something much more than diffusion here. Choices include gels that include ND and color correction (expensive, but frequently the best way), black visquene to black out the windows completely, shooting at night, parking a big truck so that it shades the windows, shade cloth (inexpensive, but sometimes a problem if you don't have good distance between subject and window).

Problem number 3 - color temperature of the windows. This won't be a problem if you had to correct your tungsten to cool white fluorescents. Otherwise, frequently it is OK to have the windows go blue if they are in the background and not a significant source of light. Sometimes even OK if they are providing backlight. If not, there's not many alternatives to gelling the windows to correct the temp.

The best advice I can give is: Don't plan on solving these problems 1/2 hour before your shoot. Get in there and shoot and test, especially since it seems like this is a learning experience for you. You may want time to try some different approaches.

P.S. You say the north windows won't be in the shots. Will you not be doing audience cutaways for the meeting scene? You've not written about the content, but in many/most cases, an audience will get significant cues on how they think/feel/respond from looking at images of other people thinking/feeling/responding.

Thanks Seth. Advance testing isn't possible due to security (this is inside a state prison) with video access granted through rare, special permission. Another reason to get this lighting as right as possible. However, I have been to the site & know what to expect otherwise. (Can't take in cutting utensils to trim film materials either.)

Here's a new thought (still welcoming insights & tips). Treat lighting separately for the interviews & meeting. Shoot interviews in the afternoon taking advantage of daylight as primary source, gel my lights as auxiliary sources (would like to pick up sense of "where we are" with room in background). But for the evening meeting, totally block the windows and gel my lights as supplements to the room fluorescents as primary source. See any flaws with this approach?

I do plan for some audience shots, but think the actual windows can be kept out of frame - though the color temp issue is still a factor. I'm thinking that material to completely block the windows is looking like the best option considering all the windows that impact the video lighting. And this could be put in place more quickly during set up than film or netting - which was my first train of thought. Several along to help with this task during the dinner break.

Just my take, I wouldn't really worry about the windows and houselights for the interviews, use your lights and kill the houselights, they should obliterate any of the incoming sunlight, if not, take some foamcore and make quick custom covers for the windows.(given the location though I don't know if you could bring in a cutting utensil, but maybe double sided tape)

As for the meeting, leave the house lights on, and use the ceiling to bounce the light to fill in. Depending upon the number of people in the meeting, and the number of lights, it could get pretty warm in there.

just off the top of my head. you can only do what you can do. ;-)

a couple of options - first pick a color temp, then match the wrong light source to the right one.

go 3200k
buy a roll of CTO ND1, that'll cost you around $120 for 48" wide by whatever long. cut it into peices 48"long which should cover the windows. I say use the 48" length size as that will work for reuse later pretty well on normal size windows. tape it up outside. then at least your window light will be in the ball park of 3200. you can bounce the tungsten inside for the group shots, turn off the flo lights.

go 5600k
you can also just rent a 575 or 1200 HMI or two, bounce them inside, use chimeras, bounce on white cards, ect. I'd look to get color correct sources to start with. even rent a pair of 4X48" kino's ( or get a pair of richard's lights ) and turn off the interior flo lights as you'll not really know what color rendition they will have, but usually not great.

another option is to put frost on the exterior windows. precut into 48X48 peice. diffusion is around $80/roll. 1/2 frost - you can always double it. then go available light with the windows servering as primary.