Which type of cones contributes the least to the photopic spectral sensitivity curve?

Which type of cones contributes the least to the photopic spectral sensitivity curve?

• A. M-cones
• B. L-cones
• C. All contribute equally
• D. S-cones

Answer: (D)

Under bright lighting, how bright we perceive different wavelengths is driven mainly by the signals from the cones, especially the L- and M-cones. These two cone types respond best in the green-yellow part of the spectrum, so the photopic spectral sensitivity curve (the luminosity function under photopic conditions) is shaped largely by their combined input. S-cones, which are most sensitive to blue light, contribute far less to this luminance signal because there are fewer S-cones and their input is given much less weight in the luminance pathway. The result is a curve dominated by L- and M-cone input with relatively little contribution from S-cones, which is why the blue region is not as prominent in photopic luminance perceptions.

Under bright lighting, how bright we perceive different wavelengths is driven mainly by the signals from the cones, especially the L- and M-cones. These two cone types respond best in the green-yellow part of the spectrum, so the photopic spectral sensitivity curve (the luminosity function under photopic conditions) is shaped largely by their combined input. S-cones, which are most sensitive to blue light, contribute far less to this luminance signal because there are fewer S-cones and their input is given much less weight in the luminance pathway. The result is a curve dominated by L- and M-cone input with relatively little contribution from S-cones, which is why the blue region is not as prominent in photopic luminance perceptions.