The Human Eye
In my nerdiness, I've been researching the ASA equivalent of the human eye and I've found that the eye's sensitivity can't really be quantified like that. No surprise really as our eyes are able to adjust to vastly different lighting conditions. There's a detailed description as to why here:
However the latitude and "frame rate" of the eye can apparently be quantified and has been measured at about 1,000,000:1 or 30 stops operating at the equivalent frequency of 60 frames per second. This is the extended dynamic range of the eye which accounts for its ability to resolve in both extreme brightness and low light. The typical working range for most people though is 30,000:1 or about 15 stops. Additionally, people without color vision problems can discern roughly 10 million colors. Very interesting stuff.