A proof is useful only when everyone agrees what it is intended to predict.
Match proof to risk
A loose laser proof can check content and pagination. A calibrated contract proof predicts process color to a standard. A press proof tests the actual production system but costs more.
Use the right light
View critical proofs under a recognized daylight condition and avoid mixed illumination. Optical brighteners and metamerism can make the same sample change under different lamps.
Annotate approval
Record the proof type, date, version, viewing condition, acceptable tolerances, and any approved exceptions. Do not rely on a casual message saying that color looks fine.
Keep a reference
Retain the signed proof and final production file. If a rerun differs, those references let the printer diagnose whether the change came from data, substrate, process, or expectation.