Darkroom fogging affects which portion of the density range most?

• A. Toe
• B. Mid-density
• C. Shoulder
• D. Base-plus fog

Answer: (B)

Darkroom fog adds a fixed amount of density to every part of the film (base plus fog), effectively shifting the entire density range upward. The mid-density portion of the film is where diagnostic information sits most often, because it lies in the range where moderate exposure differences between tissues produce visible contrast. When fog increases the overall density, those mid-range differences become less distinct, so the detail in this region is degraded the most.

The toe (low-density, underexposed areas) is already near the base-fog level, so adding fog doesn’t change those shadows as noticeably, and the shoulder (high-density, near saturation) is already limit‑blocked—further density adds little useful contrast there.