A histogram in digital radiography refers to the:

• A. bar graph of the distribution of signal intensities
• B. number of brightness levels that can be assigned to a pixel
• C. size of digital matrix
• D. range of the exposure values that can be detected by the receptor

Answer: (A)

A histogram shows how the pixel values (signal intensities) are distributed across the image, displayed as a bar graph where the horizontal axis represents grayscale levels and the height of each bar indicates how many pixels have that value. This visualization lets you see whether the exposure produced a balanced tonal range or skewed too dark or too bright, and it’s used to help optimize brightness and contrast after processing. It’s not about how many brightness levels a single pixel can display (that’s related to bit depth), nor about the physical size of the image matrix, nor about the detector’s overall range of detectable exposure.