Since video extensometers measure without making contact, you need markings in order to set an initial gauge length. Based on this, the change in displacement is measured and the strain calculated. This is often still done by marking the specimen: by adding dots, sticking on markers or other marking options that are part of the specimen preparation process. Faster and easier is the mark-free measurement based on blue contrast light technology at ZwickRoell. Here, virtual marks are placed on the specimen image using software. Efforts required for specimen preparation are eliminated.