Not all cameras white/black balance properly. Learn how to use a paintbox and waveform/vectorscope to do it manually.
Every HD and video camera is different. Period. As often as manufacturers say their cameras match out of the box, they never do. (Panasonic comes very, very close, but still–shooting with more than one camera at a time requires a video engineer/DIT on set or post color correction.) Many rental houses will tweak their cameras to their own specs, and the most common tweak is white balance. Some rental houses will set their cameras so they white balance as neutral as possible, and some cheat the balance so it favors the warm side. One production company I used to work with never actually maintained their camera, so it always white-balanced bright orange.
My favorite white balance setting is “preset”, because more often than not white balancing under various shooting conditions can get you in a lot of trouble. If I know the camera, and I trust the preset white balance to give me respectable results for both tungsten and daylight environments, I’ll spend 99.9% of my time in preset. But–if I have a paintbox and a DIT, the DIT will usually do a manual white balance, which neutralizes the image in preparation for whatever look we are going to apply. I think it’s important to know how to do this, so I’m going to share what little knowledge I’ve gained by looking over my DIT’s shoulder for a number of years.
Hopefully we all know the “white/black/white” balance trick. Video black is a mixture of colors, and it is crucial that we black balance the camera because the color of black interacts with white. A bad black balance will do a lot of bad things to an otherwise pleasing picture, such as turning blond hair green. The traditional method is to white balance the camera first (filling the frame with a known white material lit by the dominating light in the scene), then black balance, and then white balance once more. If you’re watching the Kelvin temperature in the viewfinder you’ll often see a different value appear for the second white balance, and that value will be the proper one. (Tip: it’s best to white and black balance the camera in auto iris mode. Move the switch on an ENG-style lens from “M” to “A” to white/black/white balance, and then move it back to “M” when you’re done.)
A manual white balance is much more accurate and relatively easy to do. You’ll need a paintbox and a waveform/vectorscope. A chip chart is helpful but optional. Make sure the lens is switched to “A” so that you can control it from the paintbox, and aim the camera at a known white source lit with the light you want to balance to. Use the waveform in IRE or luminance mode to set your exposure: put white at around 90-100 units using the iris control. On your vectorscope you’ll notice a white fuzzy dot that should be near the center of the scope but is typically skewed in one direction away from center and toward the outer color boxes. That shows you how your white balance is skewed. Using the red and blue gain knobs on the paintbox, move the fuzzy dot until it is dead center on the scope. Once you get it close you’ll want to zoom in on the scope in order to make sure the fuzzy dot is perfectly centered. Congratulations! You’ve just white balanced!
Black balancing is very similar: close the iris all the way and move the small dot on the screen to the center of the vectorscope using the red and blue pedestal knobs. After doing that, open the iris again and make sure the fuzzy white dot hasn’t moved from dead center. If it has, move it back again using the red and blue gain knobs.
It may be helpful to set your pedestal while the iris is closed. Switch over to the waveform monitor and, with the lens closed, place the flat line representing black at 7.5% (for NTSC) or 0% (HD).
It’s possible to use an 18% gray card instead of white to white balance. Tone isn’t as important as using a known color neutral reference. Kodak gray cards work very well for this purpose, although chip charts or a clean piece of foam core (also known as “poly” to our readers in the UK) work just as well or better.
That’s it. You’ve now completely neutralized the camera for your current lighting conditions and you’re ready to either shoot or create a new look from your base settings.
Go to page 2 if you want to learn how to manipulate gamma and white balance using only a waveform monitor.
A chip chart will offer a few additional options. Most chip charts have two gray scales, one above the other with the chips moving from bright to dark in opposite directions. When viewed on a waveform this creates two opposing “stair step” patterns that meet in the middle of the screen. Using the iris control, place white at 100% and black at the proper pedestal value (7.5% for NTSC, 0% for HD). The point where the stair steps cross is your gamma mid-point, or “crossover” point. “Normal” gamma sees the crossover point in the middle of the waveform scale, around 50%. This method provides an objective way of seeing where gamma is set, in case you decide to manipulate gamma to create a look that you’ll have to match at a later date. (Manipulating gamma has the effect of stretching out tones on one side of gamma and compressing tones on the other. For example, moving the gamma crossover point down stretches out the highlights and compresses the shadows.)
It’s also possible to manually white balance on a chip chart using only the waveform monitor. Place the waveform monitor in “flat” mode. (The “flat” option shows color saturation, while “IRE” shows luminance.) Using the red and blue gain knobs on the paintbox, make the horizontal stair steps as narrow as possible. When you can’t make them any thinner, you’re white balanced. If you use this method I suggest switching over to the vectorscope to make sure the fuzzy white dot is centered.
Knowing tricks like these has saved me on a number of occasions. If you have the tools and a little bit of time, these techniques will ensure peace of mind when working unfamiliar gear or under strange lighting conditions.
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