Inside the booth
Place a grey reference at the same light as the portrait subject
A reference is useful only when it receives the same illumination.
A white card beside the camera may sit in different light from a guest. For a meaningful white-balance check, put a neutral reference where the face will be and keep the light path unchanged.
Position the reference correctly
Hold the neutral card at the subject plane and angle it to receive the same key and fill light. A reference near the camera can be shaded or reflect a different source. Capture it within the first frame of a controlled test, then remove it before the portrait.
Evidence: Camera manufacturer guide
Avoid clipping the card
Expose so the card retains tonal information rather than becoming featureless white. If the camera offers a preset white-balance sampler, use the manufacturer’s instructions and confirm that the result stays stable across the sequence.
Keep a reference image
Save the test with lighting and camera settings in its filename or log. If another lamp or dimmer is introduced, make a fresh reference capture. A neutral card can help set white balance but does not evaluate the full spectral accuracy of every colour.
Sources & further reading
Sources for the specific facts and product descriptions above. Our worked examples, interpretations and practical suggestions are original editorial guidance.
- Nikon, Flash Points: The Control of LightCamera manufacturer guide
- CIE, Position Statement on CRI and Colour Quality MetricsInternational lighting body position statement