Large visible differences in brightness are defined as

• A. Long gray-scale, high contrast, and many shades of gray
• B. Short gray-scale, high contrast, and few shades of gray
• C. Long gray-scale, low contrast, and few shades of gray
• D. Short gray-scale, high contrast, and many shades of gray

Answer: (B)

Large visible differences in brightness come from high radiographic contrast. This happens when the image uses a short gray-scale—only a few distinct gray tones—so the brightness jumps between neighboring densities are large. That combination produces pronounced edges and strong differences in brightness across the image, which is why “short gray-scale, high contrast, and few shades of gray” best fits. In contrast, a long gray-scale has many shades and smoother transitions (lower contrast), and the other pairings mix conflicting ideas (e.g., many shades with high contrast or few shades with low contrast), which wouldn’t yield large brightness differences.