If I Change a Term on a Contract without Notice before Both Parties?

If I change a term on a contract without notice before both parties sign, and get both signatures, is this legal?

What you are proposing is merely some evidence that tends to prove that there was a contract created and maybe that is enforceable (assuming all of the contract is present, clearly legible, and that no later changes or amendments were made). There is a principle in US law known as the "best evidence" rule -- which permits only the "best evidence" of a fact under dispute to be admitted. If you have a video of a contract being signed, that's the least reliable bit of evidence (who's there, are all the terms clear in the video, etc.). If you have a photo of the contract, that's a bit better (assuming all the contract terms are clear, and the signatures are as well). If you have a photocopy of the contract, that's even better, as the document itself can be reviewed by the fact-finder (and opposing party). But if someone in the case has the original contract to put into evidence, none of the other pieces of evidence are likely to be admitted (unless t contradict the "original" that's being put into evidence). Contract law is rather complex and convoluted, even in the simplest of cases -- and the fact that you're using terminology that's meaningless (a photo isn't considered "legal" nor is the contract that it's a photo of -- it's "evidence" of the existence and contents, nothing more) -- seems to indicate to me that you'd be better off reviewing your matter with a licensed attorney in your jurisdiction than asking online forums for assistance.