At a minimum about 12 stops, although you won't be able to find concensus on this. Some sources say 1:1 billion! Google "dynamic range of human vision".
I was going to say 10 stops. I believe you will find it quite difficult to measure a range since the human eye and brain auto adjusts for brightness levels.
Discussion
3 repliesThanks in advance.
Neville Bulsara
http://www.nevillebulsara.com
Travel and documentary photography