Color Casts Explained

A color cast is an unwanted tint in the image due to the lighting, the white balance of the video camera, or the type of film stock used given the lighting conditions during the shoot. Color casts exist because one or more color channels is inappropriately strong or weak. Furthermore, color casts aren't usually uniform across an entire image. Often, color casts are stronger in one portion of the image (such as the highlights) and weaker or nonexistent in others (the shadows, for example).

If you examine an image with a color cast in the Waveform Monitor set to Parade, you can often see the disproportionate levels of each channel that cause the color cast when you examine the tops of the waveforms (representing the highlights) and the bottoms of the waveforms (representing the shadows).

Figure. Image with color cast and its parade scope graph.

Note: For clarity, the Parade scope is shown with the tinted red, green, and blue waveforms that appear when Monochrome Scopes is turned off in the User Prefs tab.

When Is a Color Cast a Creative Look?

It's important to bear in mind that color casts aren't always bad things. In particular, if the director of photography is being creative with the lighting, there may in fact be color casts throughout the tonal range of the image. It's important to distinguish between color casts that are there either accidentally or because of conditions of the shoot and the stylistic choices made when lighting each scene. In all cases, clear communication between the director of photography and the colorist is essential.