Protocols for presenting light stimuli (including test stimuli and masking-cone stimuli). (a) An mRGC stimulus with masking stimuli flickering with contrast of ±0.30 modulation at 20 Hz. The stimulus to the mRGC varied from background (B) to high (H) with contrast of +0.50 modulation for 250 msec. (b) A cone stimulus with the masking stimuli. The stimulus to the cone varied from background (B) to high (H) with contrast of +0.30 modulation. Each measurement was repeated 30 times.