Calcium tungstate intensifying screens require films sensitive to which color band?

• A. Blue-Violet
• B. Blue-Green
• C. Red
• D. Infrared

Answer: (A)

The concept being tested is matching the screen’s light emission to the film’s spectral sensitivity. Calcium tungstate intensifying screens emit blue light when struck by X-rays, so the film used with them must be sensitive to blue-violet wavelengths to respond efficiently. This blue-violet sensitivity allows the film to record the image with lower exposure and good contrast, since the emulsion is optimized for that light. If the film were sensitive to red or infrared (or to blue-green) the screen light wouldn’t be absorbed efficiently, leading to poorer image density or the need for higher exposure. Modern rare-earth screens emit green light and require green-sensitive film, but calcium tungstate screens specifically use blue-violet sensitivity.