When switching from a 400 RS film screen combination to a 200 RS system, one should expect

• A. An increase in spatial resolution
• B. A decrease in spatial resolution
• C. No change in spatial resolution
• D. Increased patient dose

Answer: (A)

Switching from a faster to a slower film-screen system changes how detail is recorded. RS (screen speed) reflects how much light is produced during exposure; higher speed systems emit more light but blur details, while lower speed systems emit less light and preserve fine detail. Moving from 400 RS to 200 RS means using a slower system, which reduces light spread and improves the sharpness of edges in the image. That improvement in edge definition and reduced blur translates to an increase in spatial resolution. Keep in mind that to achieve the same image density with a slower system, exposure would typically need to be increased, which can raise patient dose if technique isn’t adjusted.