Figure 6B. Conversion of light intensity to cone response. Typical light sources are broad-band - they radiate photons having many different wavelengths. The plot on the left is a quantal flux distribution from a small patch of blue sky overhead near dusk. The plot on the right is an absorption spectrum like that of Figure 6A, only it is for the human short-wave sensitive cone rather than the rod. The final plot is merely the data from the first two plots multiplied together. The response of the short-wave sensitive cone is essentially proportional to the integral of the data in this plot (after correcting for other effects such as the absorption by pre-retinal media; for example, the human lens strongly absorbs most light with wavelengths shorter than 400 nm).