In low light conditions, the human eye is roughly equivalent to ISO 800 in photographic terms.
While the human eye doesn't have an adjustable ISO setting like a camera, it possesses a remarkable ability to adapt to varying light levels. This adaptation involves several mechanisms, including changes in pupil size and adjustments in the sensitivity of the retina's photoreceptor cells (rods and cones). When light is scarce, the eye's mechanisms work to amplify the incoming signal, effectively increasing its sensitivity.
- Quantum Efficiency: The eye has a quantum efficiency in low light of about 0.083.
- Threshold: The 50/50 threshold is about 72 photons (about six photoelectrons).
- Light Perception: You can see a scene of about 0.1 lux.
- Exposure Value: That's about EV -4 at ISO 100 or EV -1 at ISO 800.
This means that in very dim environments, the eye gathers and processes light in a way that mimics the sensitivity of a camera set to approximately ISO 800. Therefore, while not a direct setting, the eye's low-light performance can be compared to this ISO value.
