Quote Originally Posted by RalphLambrecht View Post
You said you measured 4s at f/16 (are you sure, it wasn't 1/4 s at f/16).
FWIW, I grabbed my Luna Pro and set it at 200. My well lit basement rec room couch read 2-3s at f/16. The much dimmer lit (it is night) living room couch gave 60s at f/16.