In digital radiography, what does bit depth influence?

• A. Spatial resolution
• B. Contrast resolution
• C. Exposure latitude
• D. Image noise

Answer: (B)

Bit depth controls how many grayscale levels an image can display. Each pixel’s value represents a brightness level, and more bits per pixel mean more possible shades of gray. When you have more gray levels, subtle differences between tissues (their densities) can be distinguished more clearly, which improves contrast resolution.

Spatial resolution, on the other hand, is about how small a detail can be seen—it's determined by pixel size and the sampling and geometry of the detector, not by how many gray shades you have. Exposure latitude refers to the range of exposures that still produce diagnostic images and is tied to the detector’s dynamic range and processing, not the bit depth. Noise is related to photon statistics and detector performance; while higher bit depth can reduce quantization effects in flat areas, the main driver of noise is exposure and system noise, not the grayscale count per se.