Color Cast

A color cast is an unintended, often unwanted color shift affecting an entire image or substantial portion of it, where what should appear neutral (gray, white) instead carries a tint toward red, green, blue, magenta or another hue. Color casts arise from various sources: incorrect white balance during capture (the most common cause), mixed lighting on set (interior tungsten plus daylight from a window), reciprocity failure in long-exposure stills, faulty filtration, color spill from nearby objects, or codec quantization in 8-bit chroma. Color casts can be intentional too — a colorist may deliberately introduce a warm cast for golden-hour memory or a cool cast for sci-fi atmosphere — but the term usually denotes a problem to be fixed. Detection methods include: examining a known-neutral reference in the frame (gray card, white shirt, asphalt), using the parade waveform to check if R, G and B traces match in shadows and mid-grays, or using the vectorscope to check if neutral regions cluster at the origin. Correction is done with the white balance picker (sample a known-neutral point), with primary color wheels (shifting lift/gamma/gain in the opposite direction of the cast), or with HSL qualifier (isolate the cast color and shift only it). Persistent casts after grading often indicate a deeper issue — a faulty in-camera LUT, mistaken IDT in ACES, or incorrect color space tag on the source file.