Report "4.5, regardless of focal distance of the zoom. This problem occurred after I disassembled part of the lens (from the front part), as some of the internal groups was very dirty, which was affecting my pictures (my suspect was fungus, but fortunately that was not the case - I found out to be the lens close to the aperture blade, maybe it was excess of oil...). I also tried to open the back part, but I gave up soon.... But I'm afraid that I touched something I shouldn't on the circuit board"