http://www.nikonchat.com/nikon-image-authentication/
Nikon Image Authentication D200 – what does it mean?
It has a setting called "image authentication" and can be turned on or off …. What to do?
I leave mine on. You do not have the largest file any thing it does is prove or disprove that any of the original images were manipulated in any way. This is important when the image is being used as evidence in court or if someone tries to prove one of the pictures published by a media has been manipulated. This feature can provide baseline demands authenticity and protect they can from the start and provide the courts with valuable admissible evidence
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