That won't stop you from visually identifying that they are the same, then just looking at the block-chain to see which hash was published first (and thus the real photo).
That right there could be a pretty expensive system to maintain and it isn't ideal to distributed across a bunch of blockchain participants, it probably has to live in a Kodak server farm somewhere.
What’s the point of a decentralized system if a trusted third party decides which images are visually equivalent? Just use that third party to register the image with in the first place, rather than in a blockchain, since that party gets to invalidate your image-hash in the chain anyway (in case your image is deemed visually equivalent to an image earlier in the chain).