Involved in repair of UV radiation-induced DNA damage. Catalyzes the light-dependent monomerization (300-600 nm) of cyclobutyl pyrimidine dimers (in cis-syn configuration), which are formed between adjacent bases on the same DNA strand upon exposure to ultraviolet radiation. cyclobutadipyrimidine (in DNA) = 2 pyrimidine residues (in DNA). Binds 1 FAD. The FAD is in its reduced state. Binds 1 F420 non-covalently per subunit. The F420 is in its oxidized state. Belongs to the DNA photolyase class-2 family.