What are the three main ways to take measurements using an optical comparator? One of the incredible capabilities of an optical comparator is that it can complete measurements in numerous ways, depending on what you are measuring and the size of your part. One measurement technique used with optical comparators is to directly compare the projected image created to measurement units such as a ruler or protractor. These image measurements are easily converted back to the corresponding measurement of the part because the level of magnification and exact location of the part are known. A second way to measure with an optical comparator is to use screen rotation. Screen rotation utilizes a marked zero point on the image in order to measure various angles on the image, which are then converted back to corresponding angles on the part. A third common measurement method involves using measurement by motion. Ideal for larger parts that cannot be completely projected at once, measurement by motion requires the operator to move the worktable or use a sliding fixture built right into the machine. Optical comparators are great tools that can do a range of measurements for a range of parts.