Which of the following can produce film fog?

• A. Wrist watch
• B. Exposed LED electronics
• C. Smoking in the darkroom
• D. All of the above

Answer: (D)

Film fog is unwanted exposure on radiographic film that raises base density and lowers contrast, coming from sources other than the intended patient exposure. A wristwatch with a luminous dial can fog film because many older dials use radium; the radioactive material emits radiation that can reach the film even when the watch isn’t in the X‑ray beam. Exposed LED electronics can fog as well if light leaks into the film or processing area and exposes the emulsion, since the film is sensitive to light in certain wavelengths. Smoking in the darkroom introduces smoke particles and fumes that can cause chemical fog during development or deposit on the film, producing a uniform veil of density. Because each of these can introduce unwanted exposure or chemical effects, all of these sources are capable of producing film fog.