Video cameras are at an eternal disadvantage to the human eye and brain. No lens is as sophisticated as the eye, no set of electronic controls can process the volume of adjustments the brain makes so effortlessly.
Take light and color for example. As we travel through the world, we are bombarded by an ever-changing array of light sources, electromagnetic waves, and color temperatures.
Yet as we move from bright sunlight through a fluorescent hallway and into a candlelit sanctuary, everything seems to be color correct. The eye and brain seamlessly compensate for the different light sources — an automatic function that manufacturers spend millions trying to duplicate in the factory preset that controls a camera’s white balance.
In manual mode, a director of photography essentially teaches a video camera how to see each new source of light and reproduce color accordingly. Under each new lighting condition, the DP holds a white card in front of the camera, allowing it to recalculate the all-important 1:1:1 ratio for red, green, and blue to reproduce neutral white. (Or the version of white that the DP is using. There is plenty of variation in what passes for white cards. Each tonal variation will produce a slightly different white balance. I’ve seen DPs use everything from a milk carton to a T-shirt to white balance. It depends on how precise you want to be.)
With the card — or T-shirt or milk carton — in front of the camera, the operator chooses the correct filter setting on the camera (tungsten or daylight) and depresses the white balance key. The camera electronically adjusts the video amps of the red, green, and blue CCD chips so that the card appears white, with no color tones. The card is removed, and colors in the scene appear true to their hue. Lighting conditions change as the sun gets lower in the sky, as clouds come and go, and as tungsten and sunlight are mixed, so taking frequent white balances is necessary to keep colors uniform from scene to scene.
Hot lighting for cool color balance
So what is the trick to getting the white balance right for a particular type of lighting? Technically speaking, it goes back to ROYGBIV — the visible spectrum of red, orange, yellow, green, blue, indigo, violet, and all the colors in between. The Kelvin temperatures of individual light sources correspond to colors on this spectrum, hence the term color temperature. Without adjustment, the camera will see the color of objects differently based on the color temperature of the lighting.
For example, the most common color temperatures we work with in film and video are: 3200 degrees Kelvin for tungsten lighting instruments (Mole Richardson, Arriflex, Klieg, and Lowel) and 2800 degrees Kelvin for regular household lamps. The sun, of course, can also be a light source. It has a wide range of Kelvin temperatures depending on the time of day, the time of year, cloud cover, smog, and other changing elements. High noon in the Virgin Islands can see the color temperature soar to more than 12,000 degrees Kelvin. But on a typical afternoon in Chicago, it’s around 5600 to 6300 degrees Kelvin.
On the chart on page 44, you can relate these temperatures to visible light. Red is on the lower end of the spectrum, and blue is at the higher end. The camera, through its white balance function, filters out excess blue or red in a scene, bringing the norm back to what we expect to see on the TV monitor.
This is all well and good if you’re dealing with one type of light source on a set (for instance, in a studio where all the lighting instruments are tungsten/halogen at 3200 degrees Kelvin). But what if you start mixing light sources, adding HMIs or real sunlight to the scene? How do you get the right white balance then?
Typically, most video engineers will try to balance all of the lights so they are at or near the same color temperature using color-correcting gels on the lights or windows. To correct a tungsten lamp for daylight, add a blue gel over the light. To bring the sunlight streaming through the window closer to tungsten/halogen lights, add an orange gel to the window.
This is the norm, but it’s not always in the best interest of art to follow the rules. “As long as you know the rules first, feel free to break them” has long been my motto. Look around. Reality is not always in color balance, nor should it be.
I like to mix and match light sources in much of my work, including the simplest of interviews. I will often light a person in front of a sunny window with a tungsten light, but let the outside go blue. Many times, my key light is tungsten and my backlight is HMI, giving the interview subject a warm skin tone but leaving the highlight on their hair a bluish tint. Reverse this, and key with HMIs and backlight with tungsten to give the hair a very warm halo effect.
Always be aware of hair color and skin tones. Experiment. Try different light sources front and back. Gel the lights and try various white balances. Creativity is often satisfied by chance. For instance, try shooting on a bus or subway train at night, letting the green cast of the interior fluorescents contrast with the tungsten street and car headlights as they flash by. Then shoot the same scene, but white balance for the interior of the bus and see what happens to the storefronts.
Many times, lighting designers will insist on lamping practical lighting fixtures (table lamps, floor lamps, ceiling fixtures, and other lights used as props in a scene) with color correcting bulbs. I prefer to let them appear warmer than the set lights and therefore use the original household bulbs (2800 degrees Kelvin). Using a dimmer on the practical lights will give them an even warmer glow.
I’ve seen scenes where candlelight was the key source totally ruined by white balance. Rather than being a warm, orange glow reflective of burning wicks, a tweak of the white balance button brings the scene back to a pale orange-white with no life or sex appeal to it. Candle-lit scenes can also be enhanced by adding an orange or straw gel to tungsten lights or by dimming them with an in-line dimmer.
There are certainly times when color accuracy is extremely important. Industrial and medical applications often require true color renditions. If the liquid pouring into a beaker in a chemistry lab should be light blue and not purplish blue, then it’s important to accurately render these colors to video. Here’s where a color temperature meter and an accurate white balance are handy. Color temperature meters are expensive tools, but indispensable when dealing with multiple light sources.
But keep in mind, although white balance is a science, it is also an art, and good science is not always good art. For example, years ago in the naivety of my youth, I was working with a talented yet aggressive lighting director. It was a night scene in a parking lot and I was using HMIs as my primary light source. The fluorescents inside a storefront had been carefully gelled with minus green to match the HMIs when my lighting designer shut down production for two hours to cover the tungsten car headlights with a blue color correction gel to bring them to white. The delay cost several thousand dollars.
Later in my career, I learned that letting the headlights go slightly orange would have added another dimension to the scene and been more pleasing to me, the DP, and probably my viewers.
So what happens when the white balance of footage is off dramatically?
One situation in which improper white balance is common (and one that drives me up a wall) is shooting a television monitor within a scene. It’s amazing how few video pros realize that most television sets are balanced for daylight in the 5600 Kelvin range.
If a scene has a white person of average skin tone standing next to a television set, and that person is keyed with tungsten/halogen light, and the video camera is balanced for the tungsten light, then the TV monitor will have blue overcast. Look at just about any newscast featuring monitors in the background and they will all have this bluish tone. Even high-budget feature filmmakers frequently make this mistake. Sometimes it’s the intention of the DP to give the background TV sets a blue tone, but more often than not they don’t realize the real Kelvin value of the monitors.
There are easy fixes for this particular problem. Light the person with HMI lights balanced for 5600 degrees Kelvin, or color correct the tungsten key lights with blue gels. Find monitors that can be switched to 3200 degrees Kelvin. In any case, take a white balance directly off the TV by playing back a scene on the monitor with lots of white in it. This will give you good color rendering for all of the colors on the TV, as well as the subject next to it. Experiment. Try taking a white balance off the TV and a second one off the blue-gelled tungsten or HMI key lights to see which one looks better.
An off-white balance can also have a psychological effect on the viewer when it is used to convey different moods. In the recent box office hit Traffic, director Steven Soderbergh played with the audience by giving locations specific color tones. Scenes in Washington, D.C., were given cold blue tones, while scenes in the San Diego area were warm and lush with gold overtones.
Television commercials have done this for years and often depict the color flavor of the month. A few years ago, green was the color of choice. Last year, blue caught the advertising creative’s eye. Who knows what it will be next year. Try experimenting with different color balances for the same scene and see what effect, if any, it has on your particular audience.
So how can you trick the camera to get these kinds of effects? There are times when you as DP are going to want to mislead the camera because you’re after a desired look.
Today’s cameras don’t deliver the beautiful, rich-looking warm images that older television tube cameras used to have. CCDs may have made cameras less expensive, smaller, and more reliable, but in the eyes of many video pros they have also made the pictures colder, harsher, and less pleasing. As a result, it has never been more popular to use diffusion and warming filters in front and behind the lens, as well as soft lighting techniques and amber or straw-colored gels in front of key lights.
Often, the DP will take a white balance with no filter in front of the lens or on the lighting instruments and then will add these warming elements for the desired effect. Another way to trick the camera is to white balance through a colored gel. Holding a piece of blue gel in front of the lens makes the camera think there’s too much blue in the scene, and it will compensate by adding warmer tones to the image. These gels come in various densities, so the amount of warmth added can be your choice. If the DP wants a colder look, an orange or amber gel is held in front of the lens during the white balance.
As always in the video biz, using good tools can make a big difference in your results. Two of the leading manufacturers of color-correcting materials, such as gels and filters, are Rosco (www.rosco.com) and Lee (www.leefilters.com). Also, there’s a new product on the market that is gaining quick acceptance. It’s called Warm Cards — a set of tinted cards that allow camera people to trick the white balance of their camera into delivering a warmer, more pleasing look.
Unlike other warming techniques described here (which may give haphazard results), using Warm Cards is a precise way to get a consistent warming effect. There are no gels to hassle with, no lighting to worry about, and no filters to screw on and off the lens every time a new white balance is needed. Warm Cards come in three grades and are as easy to use as an ordinary white card. Check out the options at www.warmcards.com.
In closing, choosing the right (and there really is no such thing as correct) color balance is up to you and the folks who put up the money for the production. After all, what are blue sky and green grass? It all depends on how you want to look at it.
Bill Miller has been directing and shooting films and videos for nearly four decades, with work appearing on several major and independent television networks. He recently directed his first dramatic feature-length film, Bluff. Visit his website, www.directorsnet.com/miller/index.html, or email him at firstname.lastname@example.org.