Merry Christmas to all. I am using a Nikon 70s with the SB-800. I normaly shoot in "A" mode but I wanted to use "S" mode to contol the flash lighting better, when I did this I had control of the shutter speed but the aperture would not change, it went to the widest aperture 3.5 and stayed there. The secondary wheel would not change the aperture. What am I doing wrong. John.