white balance on the fly

[David Morgan]

I was recently in a situation where I couldn't white balance before a show. In addition, there was nothing white on stage to balance to on the fly until about 4 numbers into the show. I noted where the problem was however. Deep reds were reading as magenta (purpleish). I was finally able to find a white shirt in one of the acts and managed to get it done.
I'm playing hell in post trying to shift the purple shirt to red.

Anyone have any war stories about this? From now on, I will carry a white reflector and insist that someone hold it up so I can balance.

[Chris Nuzzaco]

You don't have to white balance on white. Any neutral shade of gray will work fine. I've white balanced on asphalt roads several times. The only time I've had problems with this though, is when its a little to dark, if thats the case, just open the aperture more and give it a go. Should work fine.

I don't always endorse electronic white balancing however. I can understand doing it for some types of shows, like sporting events and such, but for films, you should go optical to get a cleaner image.

[Bill Davis]

Originally Posted by David Morgan

I was recently in a situation where I couldn't white balance before a show. In addition, there was nothing white on stage to balance to on the fly until about 4 numbers into the show. I noted where the problem was however. Deep reds were reading as magenta (purpleish). I was finally able to find a white shirt in one of the acts and managed to get it done.
I'm playing hell in post trying to shift the purple shirt to red.

Anyone have any war stories about this? From now on, I will carry a white reflector and insist that someone hold it up so I can balance.

David,

IF you're doing your post on any modern computer based NLE, you shouldn't have that a big problem doing a virtual white balance "after the fact" on the red/magenta problem.

But don't just concentrate on the purple to red problem. If the white balance was off - it will be off for ALL colors. So work with GLOBAL changes - not just a particular color channel.

Just invoke the three way color corrector and do a side by side comparison of any common object in the pre and post white balanced footage using skin tones, the magenta fabric or whatever. But again, don't try to correct using just a single channel - try to correct using the overall white point setting. That why when one color is correct - all the OTHER colors will be correct as well.

Good luck.

[John Miller]

I like to use a coffee can lid:

http://www.enosoft.net/products/enod...iteBalance.htm

Ignore the software-specific stuff. Any app that lets you do color adjustment will work although direct adjustment of Cr and Cb is best.

[David Morgan]

thx for the responses. I get it about the gray scale. I'll remember that. doesn't the coffee lid have to have enough light on it to be useful? In addition, I usually work in theates where the camera is in the dark. I'm pointing at a lit stage.
however, what I was faced with was a totally yellow draped stage on 3 sides. Then the acts entered from the wings. Yike!

[John Miller]

Yes - that's a good point! You probably wouldn't have enough light except perhaps when the house lights are on.

However...I'm not sure how you would set a white balance anyway in a theater unless you know for sure that the lighting is white at the time. Lights have a habit of changing rather a lot in a theater!

Are you there officially and, if so, can you make some kind of arrangement with the lighting director or someone like that to help provide some suitable illumination before the show?

[David Morgan]

I'm not there regularly. It can be tough but I try to get enough time to ask the board operator to "turn em up" and then find something white to zoom in on and balance. I have a white poster board but I'm going to start using one of those matte white round reflectors that twist up in fit in a bag. for show work, most of the lights have gels etc.... on em. Don't see white too often. Problem on the last show was they only had fixed stage down lights and no operator. It was at an elementary school. No glamor here !!

[Shawn McCalip]

I always carry a piece of folded up paper from the copy machine in my back pocket. In the event that I need to tweak white balance in post, I'll bring up the "fast color corrector" and shift the master channel in the blue or yellow direction.

[Vic Owen]

David--

At this point, it sounds like you've figured it out. I've done many, many theater shows. After having to color-correct the first few, I make it a habit to carry a 2X3 ft poster board, and I have the light board op give me their "whitest" scene so I can do a white balance. It's saved me lots of time in post, and the theaters where I most frequently shoot are now aware (trained?) to the point they'll ask me if I'm ready to do the white balance right after the talent finishes their warm-ups.

[Dale Guthormsen]

Vic,

Curiously, are you moving closer to the stage to get the white balance reading or are you trying to get it from the distance the camera will be from the stage???

[Bill Davis]

Originally Posted by David Morgan

thx for the responses. I get it about the gray scale. I'll remember that. doesn't the coffee lid have to have enough light on it to be useful? In addition, I usually work in theates where the camera is in the dark. I'm pointing at a lit stage.
however, what I was faced with was a totally yellow draped stage on 3 sides. Then the acts entered from the wings. Yike!

David,

That's gonna be a problem no matter WHAT else you do.

ALL the lights hitting the yellow drape will reflect all over the stage bathing your subject in a certain amount of yellow spectrum.

So trying to pull a white balance that keeps the skin tones of the performers true while SIMULTANEOUSLY keeping the drapes true is gonna be REALLY tough.

My advice is to concentrate in post on getting the performers skin tones correct, and allow the drapes to shift to whatever color they need to in order to achieve that.

Hard situation.

[Vic Owen]

Dale--

Nope, I set it from the normal taping position, at the back of the theater; that's why I carry the larger white board. I believe that helps insure that I'm getting the same average reflected lighting that I'll get during the performance. The other colors seem to come out pretty true, using that method.