Gary, if you need a copyright, a subtle one works best as it doesn't detract from the image, particularly if the copyright is somewhat transparent.
If you are trying to advertise for business, make sure your web page is in the copyright area of the image metadata so that folks can find you.
If you are trying to protect you images from being used by others without your consent, the standard laws concerning copyright will be in your favor should you decide to take someone to court. For those that don't obey the law, the logo has absolutely no effect as it is so simply removed.
If you would like additional feedback as this has been discussed many times before at CiC, take a look here (and elsewhere in this forum).