Judging by the pic the compartment didn't need to be painted black. Contrary to that the camera ports going through the fuselage skin were of the matt black colour. So the kind of the anti-glare filter was mounted just at the lens only. However if a maintence crew decided to paint the compartment black it could have been done. But it would be, lets say, a '' filed modification" but not the factory one. Here in the shot the silver paint of the bulkhead seen and the inner side of the accessing hatch can be noticed.
Even these F24 cameras in the underwing blister for the PR. Mk.Ic dodn't seem to be in the black painted section there.