When is white not really white? When it’s headed toward an unprepared camera sensor. Understanding white balance and the colour difference between light sources is critical to getting the best look from your camera, which also makes it a crucial part of cinematography where everything in the frame needs to look perfect.
Different light sources produce different colour temperatures
A stroll through your neighbourhood at night can reveal some important differences in colour temperature among artificial light sources. As your eyes adjust to the dark, observe the different colours of light around you. Those little solar lights in the garden seem to be bluer. The light coming from the house fixtures looks more orange. That kitchen window seems almost green. Those street lights look almost pink. Your brain tells you, though, that each of them is white light.
Science tells us that light is a vast spectrum that ranges from what we see into the invisible — infrared and ultraviolet light. In between is the entire rainbow of colours, graded by colour temperature on the Kelvin scale.
On this scale, incandescent or tungsten light sits at about 3200 kelvin (or 3200 K for short). Sunlight varies as it travels across the sky but is placed generally at 5600 K. At dawn and dusk, it’s actually warmer, or more reddish. This means, counterintuitively, that it has a lower color temperature. On an overcast day, daylight has a higher color temperature, leading us to perceive it as cooler, or bluer.
- Higher color temperature = “cooler,” bluer light
- Lower color temperature = “warmer,” redder light
While your brain automatically corrects for these differences in color temperature, your camera does not.
Your camera simply records the color that enters the lens. Yes, digital cameras have an automatic white balance setting, but if your location has multiple light sources, you might get some strange results. It’s during these times that you learn the hard way that you can’t always “fix it in post.”
Getting the white balance right
The first step is learning how your camera white balances. For a typical digital camera, there will be a setting in your menu or a separate button. In DSLRs and mirrorless cameras, white balancing can be a little more complicated. Check your user’s manual for the details.
Next, you will need to find something that is white or at least neutral, like a piece of paper, and place it in front of your camera. The key is to make sure your white is being lit by the main light source. Don’t turn your camera onto a white wall, for example, that is not getting the same light as your subject.
THE KEY IS TO MAKE SURE YOUR WHITE IS BEING LIT BY THE MAIN LIGHT SOURCE.
It’s a good idea to experiment with your camera in different situations. You need to be comfortable with white balancing and know what results you will get. Try going into a kitchen and shooting a subject in the following conditions:
- Turn off all the lights and open all the window covers around noon. White balance the camera and record a few seconds.
- Try it again at dusk.
- Turn on an overhead light fixture or two and try it again.
- Close all the curtains, or wait until dark, and use all the available lights.
When you’re done, playback your video and note the differences.
Some expert advice
We interviewed John Turner, the Technical Services Manager for KLAS-TV in Las Vegas, Nevada. He attended the USC School of Cinematographic Arts and has been in broadcast television since 1985. He has done production in all types of situations, from wars and natural disasters to court cases and presidential inaugurations.
John tells us his most challenging lighting situations are theatres.
“Typically speaking, stage lighting burns me every time. Stage lighting can be a combination of all temperatures combined in one scene. So what will you set as the primary temperature?”
Most stage lights are tungsten, but not all of them. Some theatres may have spotlights that are HMI (Hydrargyrum medium-arc iodide). These are the same temperature as daylight. You may also find newer LED lights that can be changed to cover much of the spectrum. In addition, theatrical lighting can also be coloured using thin, heat resistant plastic called gels. All of this can play havoc with digital cameras.
So what does Turner recommend in a theatre?
“Balancing and balancing often will need to occur as temps will most certainly change.”
The Right Look
John Turner tells us that ultimately white balance is going to be based on the “look” that you want to achieve. “Ask yourself what is important with this image? What am I trying to say? This will help you know what is most important about lighting.”
He tells us that in journalism, the choices may be different than in cinematography. “News photographers tend to want to keep their photography as pure and as natural as possible. ‘Keep it pure’ means going with what you have and adding nothing artificial. So, what is the object you are shooting and what is the prevailing temperature.”
Look carefully at what you are focusing on and notice what light is hitting the subject. What is the most dominant light source?
Let’s say that you’re shooting in an office with a giant picture window on your subject’s side. There are also fluorescent lights overhead and a tungsten desk lamp. The dominant light source is probably the big window. Try turning off the overhead lights and the desk lamp if that is possible and white balance off the daylight from the window.
A Little Correction Goes a Long Way
How would John Tuner handle that office shot?
“I will use a light with a 5600-degree filter or gel and then white balance for an outside exposure.” He says that colour correction is the key.
You can correct lighting colour with some simple tools. One tool is the lamp or bulb in your lighting fixtures. A trip to your local hardware store will reveal a wide variety of choices in fluorescent tubes and even common house lamp bulbs. If you have a more advanced light kit, there are most likely different color temperature lamps available. Make sure that you at least keep 3200K and 5600K options on hand.
Another basic correction is the gel. A few sheets of gel on hand can be a game-changer. Place these thin sheets in front of your light to instantly change the color temperature. If you have a light that gets very hot, make sure the gel is away from direct heat — they will melt. There are large sheets of gel available to cover an entire window if that’s what you need.
Thanks to the advent of the LED lighting, there are some new lights that have adjustable temperature settings. Turner says, “They are small, powerful, take less power, color correctable with the turn of a dial and they don’t get hot. A small LED light can make all the difference in the world when those mixed-light issues arise.”
Learn the Basics
Finally, John says that being observant and always learning are vital habits. He also offers a unique perspective: “Learn the fundamentals of natural audio, lighting, composition, framing, and editing. What does audio, composition, and framing have to do with lighting? EVERYTHING. Audio has as much to do with your lighting as does the looking at a hot fudge sundae has to do with how it taste. What is being said and how it sounds will influence your lighting design, concept, and set the tone for the condition.”
So be observant of the light around you and learn from your lighting mistakes.