White balance and profiles
A white wall isn't equally white under a light bulb and under an overcast sky. The camera needs to know what light there is for the colors to come out right, and in video a color mistake is much harder to fix than in a RAW photo.
Light has color
Every light source has its own color, measured in kelvin (K). The lower the number, the warmer (more orange) it is; the higher, the cooler (more blue).
| Source | Approximate temperature |
|---|---|
| Candle | 1900 K |
| Incandescent / warm household bulb | 2700–3000 K |
| Sunrise and sunset | 3000–3500 K |
| "Tungsten" LED video light | 3200 K |
| Midday sun / "daylight" light | 5500–5600 K |
| Overcast day | 6500–7500 K |
| Shade under a blue sky | 8000–10,000 K |
White balance tells the camera the temperature of the light so that white comes out white.
Why not to use auto white balance
In photography, auto usually gets it right, and if it doesn't, you fix it in the RAW file. In video there are two problems:
- It changes during the take. If someone in a red sweater walks into the shot, auto may "correct" for it and the whole image shifts color halfway through the shot.
- It changes between shots. Two shots of the same scene with different white balance won't match when you edit them together, and you'll have to match them one by one.
Set white balance to a kelvin number and don't touch it during the scene. In daylight, 5600 K; with light bulbs, 3200 K. If you're not sure, do a manual white balance with a white or gray card and note down the value it gives you.
How to do a manual white balance
- Place a white or neutral gray card where the subject will be, getting the same light.
- Fill the frame with it.
- Use your camera's custom white balance function (usually called "Custom", "Custom WB" or shown with a card icon).
- Check the kelvin value and note it down so you can repeat it on other shots.
Mixed light: the silent enemy
A face lit by a window (5600 K) on one side and a lamp (2700 K) on the other will have one blue side and one orange side. No white balance fully fixes that. Your options:
- Turn off the lights you don't control.
- Swap the bulbs for ones with the same temperature.
- Use the mix on purpose, as in the look of a lot of modern films: warm background, neutral subject.
Picture profiles: standard vs log
The picture profile decides how the camera processes the sensor's information before saving it.
Standard
Standard profile: colors and contrast ready to publish. Easy, but it loses detail in highlights and shadows and leaves little room for correction.
Log
Log profile (S-Log3, F-Log, V-Log, C-Log…): a gray, washed-out image that keeps the maximum dynamic range. You have to grade it later, but it gives you much more room.
Log needs precise exposure (usually a little brighter than looks right), recording in 10-bit and working on the color in the edit. If your camera only records 8-bit or you're in a hurry, a standard or gently flat profile will give you better results than badly handled log, which ends up with banding and noise.
What is a LUT?
A LUT (look-up table) is a table that transforms colors. The most common one converts a log image to normal colors (Rec.709). Many cameras let you view it on screen while recording without applying it to the file. You'll see this in the color grading lesson.
8-bit and 10-bit
The bits tell you how many shades each color can store. With 8-bit there are 256 levels per channel; with 10-bit, 1,024. In a blue sky gradient, 8-bit can show visible steps (banding) if you push the color a lot. If your camera offers 10-bit, use it with log.
- Light is measured in kelvin: low is warm, high is cool.
- Set white balance manually and don't change it during a scene.
- Avoid mixing sources of different temperatures, unless it's on purpose.
- Log = more dynamic range and more work later. Better with 10-bit.
Your turn: three white balances for one face
Next to a window, film the same face with white balance at 3200 K, at 5600 K, and with a manual white balance on a sheet of white paper.
- Put the three clips one after another.
- Which one feels cold and which one feels warm?
- Turn on a household lamp and repeat. Look at the mix of temperatures on the face.