Reviewing my files from last Monday's outing with the family, I realized that they were all at 500 ISO. This surprised me because I have Auto ISO enabled for P/A/S mode and almost everything was shot in either A or S mode. Images from the previous day were fine and the only thing I did in the interim was switch batteries. Looking at the Settings (Gears)|Exp-ISO, I noticed that the ISO there was set to 500 and not to Auto. I certainly do not recall doing this, so I was wondering if I may have done something inadvertently and what it may have been. Would appreciate any help in helping me understand what happened. And of course, I should have noticed it while I was taking pictures and will pay more attention in the future.