In densitometry, what does 'Base + fog' refer to?

• A. The base plus fog density
• B. The maximum density of the film
• C. The density difference from base to mid
• D. The developer temperature

Answer: (A)

Base+fog is the baseline optical density of a film, consisting of the film base density plus the fog density that comes from processing, aging, and handling. The base is the inherent density of the film substrate, and fog is unwanted background density added by chemical fogging or exposure to light during storage or processing. This combined value serves as the reference point in densitometry; you measure densities on the film and subtract this base+fog background to obtain the true image density produced by exposure. The other ideas don’t describe what base+fog means: maximum density is Dmax, the density difference from base to mid is part of the sensitometric curve, and developer temperature is a processing parameter that can influence overall density but isn’t the definition of base+fog.