What feature can effectively decrease noise in radiographic images?

Smaller grains in radiographic film or digital detectors contribute significantly to decreasing noise in images. Noise typically arises from variations in the data captured by the imaging system, which can include both quantum noise and electronic noise. Smaller grains allow for better resolution and detail in the image, as they can capture more nuanced variations in exposure and signal. This results in a clearer image with reduced randomness, leading to an overall decrease in noise.

When considering the other options, they do not effectively address noise reduction in the same way. Higher contrast relates to the difference between light and dark areas in an image but does not inherently impact noise levels. Increased temperature might affect the performance of the imaging system but could lead to increased noise rather than reducing it. More efficient screens can enhance the speed and quality of imaging but do not directly reduce the inherent noise present in the radiographic image.