Several times I have been asked from fellow members what is proper and what protects you from people who choose to copy pictures instead of getting a new original or obtaining permission. First let me explain the difference between 'work for hire' and 'full ownership.'
If you are employed by a publication and are paid on an hourly or contractual basis, everything you shoot is owned by your employer. BUT if you are hired for a one time shoot or are a freelancer like most of us, then the copyright remains with the person who snaps the shutter...YOU.
The Copyright Act of 1976 provides protection against use of a copyrighted work by reproducing it 'in whole or any substantial part' and by duplicating it...exactly or by imitation or simulation without permission. Copyright protection extends to both published and unpublished photographs. Failure to protect copyright properly can result in a permanent loss of the copyright owner's exclusive rights to the work. Here are a few essential guidelines to keep in mind as you review the detailed discussion that follows:

1. The law provides that the photographer owns the copyright in all work completed on a freelance assignment, as long as there is no written agreement to the contrary.
2. Put a copyright notice on all of your work: (c) (year) (your name)." Don't give your work to anyone without that notice & document all invoices and include it on all paperwork...
4. On all editorial assignments, require on-page credit in the form outlined in step 2. For all other uses, require copyright protection by notice.
5. Registration in the U.S. Copyright Office is not essential, but it is definitely helpful for copyright protection. Be sure to register your most important work. You can register pictures in bulk or individually.
6. If unpublished work is registered, it does not need to be registered again when published.
7. On the back of each and every picture & slide that goes out [even to friends & family] Put your required rights protection saying :

   "This picture may not be digitally stored,altered,or re-transmitted nor transmitted in any form without the written permission and or agreement of the original copyright holder.In addition,an adjacent credit line, preferably in proper copyright form, must accompany this picture. Omission of or incorrectness in this credit is subject to additional billing".
   (c) 1995 YOUR NAME