The spectral sensitivity maximums for scotopic and photopic systems are approximately what values?

The spectral sensitivity maximums for scotopic and photopic systems are approximately what values?

• A. 555 nm for scotopic and 507 nm for photopic
• B. 507 nm for both
• C. 507 nm for scotopic and 555 nm for photopic
• D. 555 nm for both

Answer: (C)

When light is dim, vision is dominated by rods, whose pigment is most sensitive around the blue-green region of the spectrum, about 507 nm. In bright light, cones drive vision, and their combined photopic sensitivity peaks near 555 nm, in the green-yellow region. So the spectral sensitivity maximum for scotopic (rod) vision is roughly 507 nm, while for photopic (cone) vision it’s about 555 nm. The other options either swap these values or assign the same peak to both systems, which doesn’t align with how rods and cones are tuned differently. This difference also underlies the Purkinje shift, where peak sensitivity shifts toward shorter wavelengths as lighting becomes darker.

When light is dim, vision is dominated by rods, whose pigment is most sensitive around the blue-green region of the spectrum, about 507 nm. In bright light, cones drive vision, and their combined photopic sensitivity peaks near 555 nm, in the green-yellow region. So the spectral sensitivity maximum for scotopic (rod) vision is roughly 507 nm, while for photopic (cone) vision it’s about 555 nm. The other options either swap these values or assign the same peak to both systems, which doesn’t align with how rods and cones are tuned differently. This difference also underlies the Purkinje shift, where peak sensitivity shifts toward shorter wavelengths as lighting becomes darker.