Different Types of Light for Your DSLR Video
You can set your DSLR on automatic and let it adjust to different lighting circumstances, but there’s no guarantee that successive scenes in your film are going to match. That means you're better off adjusting the camera manually. That’s not necessarily a bad thing because the key to dealing with light (and making movies) is to understand it.
Video color temperature
Since the early days of color photography, colorcasts of some images have sometimes looked "off." Maybe a cityscape takes on a green colorcast, resplendent of suburban Mars, or a yellow street scene comes to resemble a view through shooting goggles.
Of course, you usually only noticed the problem after you took the picture — way after. Remember, back in the days of yore, or about ten years ago, serious photography was captured on transparency film and sent to the lab for processing. You usually didn't notice problems until the prints came back from the lab. Digital photography made capturing the subject more predictable but didn’t necessarily eradicate the problem.
That’s because there’s a disparity between the color temperature of the scene and the white balance setting. If you shot on film, you often got variations in the daylight-balance the film was engineered to capture.
With video, the onus falls on the white balance setting. So if the difference between the color temperature of the scene and the white balance setting differs, you have a colorcast.
This color of light, or more appropriately, its color temperature, is defined by a unit of measurement called the Kelvin scale. It’s named after a guy who liked holding pieces of metal over an open flame to see what color they turned at various heat settings. Apparently he was on to something, creating the measure (no pun intended) for color temperature.
This thermodynamic scale measures the amount of heat reflected by different light sources under controlled conditions. Although the Kelvin scale is a measurement of temperature, a K, as opposed to a degree symbol, follows the numbers. Color temperature ranges from a candle at 1,800K to an overcast sky at 11,000K. A warmly illuminated theater interior has a Kelvin color temperature in the high 2,000s.
|Light Conditions||Measured in Kelvin|
When the Kelvin number is lower, the image renders warmer, or more orange. And when it's higher, the scene is cooler, or bluer.
Shoot the daylight spectrum
Shooting outdoors covers a wide range of color temperatures, or more appropriately, white balance settings. As the most common light source for your movie, daylight deserves some close enquiry.
The quality of light changes continuously throughout the day. That means that both the intensity and color of the light change. Although understanding why daylight renders a certain way at a specific time is important, taking frequent white balance readings is even more vital.
Hypothetically, if you begin shooting at the crack of dawn to capture the scenes that benefit from the soft quality of warm morning light, the fact that you didn’t change your white balance setting isn’t going to matter. Sure, the scene renders warmer than normal, but it should still be flattering.
After bathing the subject in early morning light, you can move to the next scene. Now say it remained sunny in the morning: The color balance of footage renders on the warm side but still looks normal. But then clouds roll in, making it overcast in the afternoon. Without changing the white balance, you can render the scene with a cooler tone. It’s especially evident in the shadow areas.
Later in the day, say the sun breaks through the clouds. The color balance of the footage takes on an exaggerated look again (as it did in the early morning), reproducing with a warmer than normal appearance, contrasting the overcast footage that has a dominant blue tone.
Daylight has a wide spectrum, making it critical to continually adjust white balance.
Film from dawn to dusk
The earliest bits of light at daybreak reproduce with a much warmer color balance than light during the middle of the day. The quality of early morning light becomes less intense as the sun rises higher in the sky. Light temperature increases as the day goes on.
If there’s a clear sky, it stays within the daylight range (2,200K–5,500K). If it’s overcast, it can go much higher. After the sun reaches its highest point in the sky, the color temperature starts to rise, and the light gets warmer as dusk approaches.