How big does a watermark have to be to be legally recognized?

sjgcit wrote:

AFAIK a watermark in and of itself does not afford any legal protection. Copyright and registration are what you need for that.

Watermarks are mostly used for two purposes in photography :

• To mark the images in a way that allows them to be displayed for e.g. sales purposes, while hindering the usefulness of a copy of the watermark image commercially.
• To advertise the creator and/or owner of the image.

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StephenG