**Figure 5. **Parameters of Ca^{2+} turnover in cones derived from the model. **A**: Average time course of the decay of free Ca^{2+} concentration after instantaneous closure of the CNG channels. Mean of 16 cells ± standard error of the mean (SEM). The red
line is a two-exponential approximation of average data, with relative amplitudes of 0.694 and 0.306, and time constants of
51 ms and 1.57 s, respectively. **B**: Correlation of the buffering power of the fast Ca^{2+} buffer (*FB*) with the cone’s dark current. Circles mark individual cells. The straight line is a least-square linear fit to data forced
to pass through zero. The red cross marks an (imaginary) cone whose dark current and *FB* value correspond to the average of the population. **C**: Effect of *FB* value on the shape of the model response. The solid smooth line over the noisy curve shows the best-fitting model, *FB* = 43. Dot-dashed line: model response with *FB* = 11; smooth red line: model response with *FB* = 86.