How to avoid reprints of your photographs?

Question

I sell 8x12" prints with a resolution of 150 dpi and my question is: Can my clients enlarge the 8x12" print and get a good result?
All my photographs are copyrighted but some people do not respect that. What's the recomended resolution to get a good 8x12"print but not good for reprints or enlargements?.
Or can they scan the photo and make it big?
How can I avoid that?
Thanks.

Answer 1

You cannot stop people copying pictures you sell to them. There will always be people who do not respect other folks' intellectual property rights.. I can't see how you can stop these potential thieves rephotographing your prints, scanning them, etc. Just make sure that the rear is clearly stamped with the international copyright symbol ( © ). Have something attached to the back stating that unauthorised copying will result in your taking action.