Do I Need To Disclose Evidence In Advance?

So I believe that the officer indicated in his notes that he used a different gun than the one he actually used to measure my speed. If I want to bring an image of the gun that looks like the one he said he used and an image of the gun I think he used, do I need to disclose that to the prosecutor in advance of the trial or only if the prosecutor asks me for disclosure? Also would it be advisable to alter the images to hide the names of the manufacturers of each gun?