Visual testing is a basic testing method, allowing to detect surface defects of a given object. Using naked eye or optical devices with 20x zoom we can detect cracks, deformations, slagging as well as changes due to corrosion and erosion of materials. Surfaces which are inaccessible can be inspected with a boroscope, fiberoscope or a videoscope. Visual testing can be conducted at various stages of production and operation or during periodic inspections of machines and equipment. One example of a visual test is quality control of welds.