X-ray films have been designed to be most sensitive to which color in the blue-violet spectrum for use with calcium tungstate intensifying screens?

• A. Blue
• B. Green
• C. Red
• D. Yellow

Answer: (A)

The light emitted by calcium tungstate screens is blue-violet, and the film emulsion is formulated to be most responsive to that color. When blue light from the screen reaches the blue-sensitive layers of the film, it converts more photons into latent image centers, producing greater density after development. Light in the green, red, or yellow parts of the spectrum isn’t as efficiently absorbed by the film’s blue-optimized emulsion, so those colors would yield less image density and poorer exposure with this screen.