Which of the following describes fog types encountered in radiography?

• A. Development (chemical) fog
• B. Scatter fog
• C. Safelight fog
• D. All are types of fog

Answer: (D)

Fogging on radiographs is unwanted density on the film that reduces image contrast. Development (chemical) fog happens during processing when the film is overdeveloped, the temperature is too high, development time is too long, or contaminants are present. This causes a uniform darkening of the film even if there wasn’t a proper exposure. Scatter fog arises from scattered x-ray photons reaching the film; this adds random density and lowers image sharpness and contrast, especially if grids or lead shielding aren’t used effectively. Safelight fog occurs when the safelight in the darkroom exposes the film because the wrong filter, wattage, or distance allows light to leak onto undeveloped film, producing pre-exposure fog. Since each type adds unwanted density that degrades radiographic quality, all of these are considered fog in radiography.