Proving that something is a derivative work is not so cut and dry, and in your case a lawyer may not be able to successfully argue that a black and white filter

Proving that something is a derivative work is not so cut and dry, and in your case a lawyer may not be able to successfully argue that a black and white filter represents a derivative work. Even the Barack Obama Hope poster was never successfully argued one way or another as to whether it was a derivative work, and the 2 sides settled out of court.