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We see over an enormous range of mean light levels, greater than the range of output signals retinal neurons can produce. Even highlights and shadows within a single visual scene can differ ∼10,000-fold in intensity—exceeding the range of distinct neural signals by a factor of ∼100. The effectiveness of daylight vision under these conditions relies on at least two retinal mechanisms that adjust sensitivity in the ∼200 ms intervals between saccades. One mechanism is in the cone photoreceptors (receptor adaptation)^,,, and the other is at a previously unknown location within the retinal circuitry that benefits from convergence of signals from multiple cones (post-receptor adaptation)^,. Here we find that post-receptor adaptation occurs as signals are relayed from cone bipolar cells to ganglion cells. Furthermore, we find that the two adaptive mechanisms are essentially mutually exclusive: as light levels increase the …