If you are truly concerned about how your images are presented or transported,
why not just spell out it's use in a contract? With a proprietary contract you
can specify the use and have some sort of agreement for financial penalties
for it's violation.
Doesn't matter if it's TFP or general commerce.
Or, if you really want to watermark your images, why not just subscribe to
Digimarc technology (http://www.digimarc.com
). Find the plan and services
that fit your needs and you can have your unique id embedded in the images, (including print) that is invisible.
Plus, as Andy Perlman states so often that this should be a "sticky" on the
forum, how to go about copyright registration with the goverment. Goverment
registration backed with digital embedding will truly allow for all intents
and purposes provide plenty of legal firepower.
Some people complain about the costs ( as low as $50.00 per year) then go out and buy Alien Bees or new lenses or some other do-hickey that costs hundreds of
dollars but balk at protection for their photos.
These same people will talk about how valuble their images are yet fail to
do a cost benefit of this type of protection.
I've benefitted from digital watermark by several thousand dollars, simply
because the images were highly proprietary and the "thieves" did not know
they were embedded with proof of ownership till it was too late. It was
cheaper for them to settle than go to court.
If you are going to use technology, use it fully to protect yourself as well.