For screen-film systems, the commonly cited spatial resolution value is around how many lp/mm?

• A. 7 lp/mm
• B. 12 lp/mm
• C. 15 lp/mm
• D. 22 lp/mm

Answer: (C)

Spatial resolution in screen-film radiography is described as how many line pairs per millimeter (lp/mm the system can distinguish). In a standard screen-film setup, the practical limit for resolving detail comes from the combined performance of the screen (which converts x-rays to light) and the film (which records that light with its grain structure), along with geometric factors like focal spot size and distance. Together, these elements typically yield about 15 lp/mm under good conditions, which is why that value is commonly cited for conventional systems. Values around 7 lp/mm would indicate noticeably poorer detail or older gear, while around 12 lp/mm is lower than the usual standard, and around 22 lp/mm would require an unusually high-detail setup beyond the typical screen-film combination.