Fig. 2.

Detection performance is limited by Poisson variability in photon absorptions, while temporal resolution is limited by cellular noise. A: 3D surface of two-alternative forced-choice (2AFC) performance from rod responses. Blue line is the detection-limited side and the green line is the timing-limited side. B: detection-limited slice of surface in A. Open circles show performance of individual rods at 200 ms time shift. Blue circles show population performance derived from a saturating exponential fit to the data with the error bars representing the 95% confidence interval (see materials and methods). Red line is the performance of the ideal photon detector (Eq. 5). C: timing-limited performance in A at a flash strength of 4 photoisomerizations (Rh*). Population means (green points) are derived from a saturating exponential fit to the rod data (open circles). Red line is the performance of the ideal photon detector. D: temporal sensitivity of the single-photon response (resp.). Isolated single-photon responses were discriminated at different time shifts. Open circles show performance from 6 individual cells. Black line is a cumulative Gaussian fit to the data.