Which feature of the D log E curve expresses image receptor contrast?

• A. Intercept
• B. Midpoint
• C. Curvature
• D. Slope

Answer: (D)

Image receptor contrast is about how quickly density changes as exposure changes. On the D log E curve, that is captured by the slope of the curve in its useful, straight-line region. A steeper slope means a larger change in density for a given change in exposure, so the image shows more contrast between adjacent exposure levels. A flatter slope means less density change and lower contrast. The intercept just sets the base density at zero exposure, so it doesn’t determine contrast; the midpoint is simply a reference exposure point, and curvature describes how nonlinear the response is, not how much contrast appears between neighboring exposures. So the slope is the feature that expresses image receptor contrast.