· 10 min read
Your Camera Is Lying About Brightness
A camera's response to light is deliberately nonlinear, so the pixel value in a JPEG is not proportional to the light that produced it. Any intensity measurement taken before that encoding is undone is measuring the camera as much as the sample. Fixing it means linearising the response, normalising against an in-frame reference rather than trusting the illumination, and choosing a background subtraction method knowingly, because two standard methods give different corrected values on the same image.