What commonly leads to a screen or film image with low density?

A film or screen image with low density typically indicates that there has not been enough exposure to the imaging receptor, which directly affects the overall darkening of the image. When the exposure is insufficient, typically due to inadequate milliampere-seconds (mAs), the resultant density of the film or image is low because there aren't enough photons reaching the receptor to create a strong image. Therefore, selecting an exposure level that is less than what is required can lead to the desired contrast being absent, resulting in an image that is too light or underexposed.

In addition, using an incorrect mAs can lead to underexposure that can be rectified by adjusting the technique to the proper values needed for the specific examination. This highlights the vital role that appropriate mAs plays in achieving optimal image density and demonstrates the importance of understanding exposure factors in radiography.