Which metric is used to assess phototimer density reproducibility?

• A. Density reproducibility of phantom films
• B. Focal spot size measurement
• C. Phototimer density reproducibility
• D. Grid alignment checks

Answer: (C)

The phototimer’s job is to regulate exposure to hit a target image density, so the metric used to evaluate its reliability is how consistently it reproduces that density across repeated exposures. In practice, you’d expose a phantom (or a uniform-density image) multiple times with identical technique settings and AEC active, then measure the resulting density (optical density or exposure index) and examine the variation. If the variation stays within the established tolerance, phototimer density reproduction is considered good. The other tests focus on different aspects—focal spot size affects resolution, grid alignment checks address scatter grid positioning, and density reproducibility of phantom films tests general film density stability rather than the phototimer’s control of exposure.