Figure 4. Testing the validity of the cascade turnoff parameters derived from Ca²⁺-clamped responses, as described in Appendix 1. A: A cone flash response (noisy curve) fitted with the model whose key parameters were roughly restrained by average Ca²⁺-clamp data (smooth curve). B: The red line shows light-induced PDE activity β_l(t) derived from the model in A. The gray noisy line is β_l(t) derived from Ca²⁺-clamped response of the same cone to an identical flash. The curve is Gauss-filtered with a 20 ms window. A smooth black line shows the least-square fit to the gray curve with Equation (15), where A=634 s⁻¹, τ₁=0.093 s, and τ₂=0.084 s. The fit is in a fair agreement with the model-derived curve.