References | Retinal eccentricity (degree) | Stimulus duration (ms) | Stimulus wavelength (nm) | Retinal image area (mm2) | Rods subtended by target | Photons at the corneaa |
---|---|---|---|---|---|---|
Mouse | ||||||
This study | <1b | 500 | 2.2 × 10−3 | 960 | 31 ± 7 (5) | |
This study | <1b | 500 | 1.9 × 10−2 | 8350 | 67 ± 6 (6) | |
Human | ||||||
Hallett et al. (1962) | 20 | 2.6 | 520 | 2.5 × 10−4 | 55 | 90 |
Sharpe et al. (1993) | 12 | 10 | 520 | 1.8 × 10−3 | 465 | 55 |
Hecht et al. (1942) | 20 | 1 | 510 | 1.8 × 10−3 | 480 | 90 |
Hallett et al. (1962) | 20 | 2.6 | 520 | 6.5 × 10−2 | 10,000 | 100 |
↵aThe number of photons at the cornea at threshold was calculated as the product of the reported photon flux density at the cornea (in photons deg−2 s−1) multiplied by the retinal image area and flash duration.
↵bFor the mouse experiments, the stimulus flashes were generated by time-gated LED pulses, which ranged in duration from 10 μs to 1 ms to control the total flash energy. The photon flux density measured at the cornea was multiplied by the flash duration and the effective dark-adapted pupil area, 2 mm2 (see Materials and Methods). For the human experiments, target areas in degrees squared were converted to millimeters squared using relations provided in Wyszecki and Stiles (1982). Areas were multiplied by rod densities at the appropriate retinal eccentricity, as given in Oesterberg (1935).