Technically, as long as you mark your original artwork with © 1999 Your Name
, no one else may use your image to produce anything, which they then sell; this is known as common copyright law
. (If you don’t plan to sell the work, it is sufficient to use a © Your Name; if offering to sell, add the year in which you first offered it up for sale.)
If, however, someone does start selling images of your original piece, you must...more
The poor man’s copyright? No. Mailing a slide of the work to yourself so you’ll have the proof of the postmark (and you can never open it) is too hard to prove. And DNA testing is expensive. You’d spend a heckuva lot more trying to prove it than if you had just spent the 35 bucks…
The safest action is to consider...more