What to do

http://commencement.vassar.edu/2002/020526.kushner.html

Thom Hogan, on controlling ISO

"One thing people aren't catching that I need to explain a little further: why ISO boost manually and not by Auto ISO? Simple: image quality. Every time you boost ISO by a stop you lose a stop of dynamic range, which is a real image quality difference. Every time you lower shutter speed by a stop you might get an image quality difference, but generally if you're above a certain bar, you get none. Thus, if you're optimizing for image quality, you never boost ISO unless your shutter speed would compromise image quality. Most Auto-ISO systems still don't get this quite right, and it seems clear that the Reuters photographers are exerting manual control over ISO, which means that they're directly managing image quality."

from bythom.com, apropos of the PetaPixel story about the EXIF breakdown of reuters' top photos of 2012.