Quote Originally Posted by Scottm View Post
To move from f2.8 to f/4 is one stop, which is the equivalent of halving your shutter speed, or doubling your ISO setting. In the "golden triangle" of Aperture, Shutter speed and ISO settings, I believe that a 1-stop change in shutter speed will have the most noticeable impact on an image, more so than a 1-stop change in aperture, especially taking into account the recent advancements in sensor technology and available ISO settings.
It's also a difference in bokeh / DoF too.