Getting It White (The First Time)

By adjusting the white balance of the video, the red, green and blue levels are all the same and properly balanced.

WHAT IS WHITE SHADING?

We often white-shade a lens to a camera to make sure that white is really white. This involves two different processes. The first process offsets the red and blue components of the video to make sure the preset levels are correct. We do this by filling the frame with a metered white surface at true 3200 Kelvin. Then we compare the preset white balance to what our lens is producing and adjust accordingly. These adjustments are saved in a "lens file" that makes sure whenever that specific lens is used, the adjustments will be applied.

The next process of white shading makes sure that color is produced at the same level from top to bottom and left to right in your image. Some lenses, especially zoom lenses, won’t produce the same color across the full image. White shading can adjust the individual RGB color channels to correct for fall-off in one color. A situation where you can really spot a lens that needs white shading is when shooting a subject against a full-white background. If there’s a shading issue, the white background will appear to be different colors on the edges of the frame.

After white shading, the channels are flat, producing an even white color across the full image. This process is especially important when shooting with multiple cameras, since a cut would quickly reveal that there’s a color difference. White shading requires scopes and a very even field of white light, so it’s usually done at a rental house like AbelCine’s. If this isn’t possible, then you’ll need to run an Auto White Balance, which of course opens up even more questions.

WHAT’S UP WITH MY AUTO WHITE BALANCES?

Most cameras have an Auto White Balance option or White Balance Detection mode available. This option detects the white balance in the scene and adjusts the RGB values accordingly. Pointing the camera at something white that generally fills at least 50% of the frame is strongly recommended. The result will give you a Kelvin value based on the RGB adjustments the camera makes. Most cameras are fairly accurate at detecting white and should match a color meter fairly closely. If your camera is far off, then you probably have a shading issue, as discussed above, and two cameras pointing at the same white card may come up with different Kelvin values for this reason. Some cameras really don’t do a great job detecting white balance, which can lead to a lot of ugly images and frustration. Your best bet is to follow this simple procedure to keep things looking good:

1. Get a proper white or grey card. Remember that grey is just a darker shade of white, so it’s okay to use. However, it’s important get a card designed for this purpose to perform your white balance. A piece of paper or white t-shirt is going to bounce back a non-balanced white color, which could throw your balance off.

2. Put your white card in the light that you’re using on set. Lighting a white card with a light source other than what your scene is set with can throw the color balance off.

3. Fill the frame with the white card. Zoom in if you can or move the camera forward to fill the frame. Most cameras balance off the center 50% of the screen, but others will analyze the full frame, so fill the full video frame with the white card.

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