Hard Proof
A physical test print made to verify colour and tone before committing to a final print run.
In depth
A hard proof settles questions no screen can, because it is judged under the same light and by the same eye as the finished piece. In commercial printing a contract proof is a formal reference the press must match; in fine-art printing a small proof on the final paper serves the same purpose at a fraction of the cost.
Examples in practice
An A4 proof on the final paper reveals shadow blocking that the soft proof had understated.