What is the tolerance for the density difference in densitometry?

• A. +/-0.02
• B. +/-0.10
• C. +/-0.25
• D. +/-0.50

Answer: (B)

Densitometry relies on measuring optical density and tracking how much light is transmitted through a film or image. The tolerance for density difference is the allowable variation between repeated density measurements. In practice, allowing about 0.10 optical density units accounts for normal, everyday fluctuations from film processing, illumination, and scanner or densitometer drift, while still catching meaningful changes in the imaging system. A much tighter tolerance like 0.02 would be unrealistic given routine variability, and a much larger tolerance like 0.25 or 0.50 could hide genuine problems. So the accepted tolerance is 0.10, balancing sensitivity to issues with practicality in routine QA.