Canon EOS R5 C Advanced User Guide PHOTO edition - Page 185

4. Shoot a white object. Aim the camera at a plain white object, so that white fills the screen. Set the camera to manual focus ( ) and shoot so that the white object has standard exposure. The custom white balance is registered to the camera. Caution Correct white balance may not be obtained if the exposure of your image differs greatly from standard exposure. Note Instead of shooting a white object, you can also shoot a gray card or standard 18% gray reflector (commercially available). 185