Contours of constant photon number as labeled on the figure that give (𝕊, 𝕆) equivalent to 95% likelihood of distinguishing two states at FRET distances of R1/R0 and R2/R0. The contours above the diagonal include only the intensity information whereas those below the diagonal include both the interphoton time and the sojourn time information. Plot was generated for kr d=1/(10 ns),knra = knrd =1/(100 ns),kra1/(2 ns), (i)=1/2, w=100 ps, γ=10, β=1, ξ = δ = ε = 0