Don't know or use an iodine bleach, but selenium
itself split tones (i.e., tones more in the dense
areas/shadows than highlights/light areas.) The
cutting action of bleaching (again not sure about
iodine; I use farmers...)is reverse proportional
to print density (i.e., works quickly/first on the
highlights.) So, I would say it depends on the
degree of bleaching that takes place, which if
overdone can create some really strange contrast
relationships. Generally, you merely want to clear
the whites when bleaching, not reduce highlight
silver too much...