Photoshop :: Scroll Bar Not Showing Relative Size Correctly

In CS4 when I zoomed in on an image, the bar at the bottom would show the size of the image now on screen relative to the full size. i.e. if I go from 50% to 100% the bar would be half the size indicating that I am only seeing half the image. At least I think that was the case in CS4.
 
Here's and example from CS6.
 
Open an image, choose "Command-0" to make it fill the window, and the percentage is 48.16%. The bar at the bottom is not there, but if it was I assume it would fill the width of the window.I select "Command-+" to zoom in, and the percentage goes to 50%. The bar now fills about 30% of the window width indicating that I have zoomed in a whole lot, but I haven't. There is only a little bit of image on either side not visible, the rest is a huge grey area extending left right, and up and down. How do I make the bar indicate the true amount of zoom, and how do I get rid of that grey area?