I posted a few days ago about images from a recent shoot being overexposed and when I looked at the EXIF data I realized that my shutter speed was set to 1/125 for all of my photos despite my using various apertures throughout the shoot. The shoot began in early evening (bright) sun and ended after dusk so there was a significant range of available light, yet photos from both the beginning and end maintain the same slow shutter. My photos from early evening are overexposed but my photos from dusk are ok. I shot in aperture priority mode (I am positive) and I double checked that both ISO and shutter speed were set on auto. What gives?