Visual inspection with or without optical aids is the original method of non-destructive testing. Many defects are cracks and can be detected by careful direct examination.
Optical aids include magnifiers, microscopes, mirrors or telescopes and also specialized devices such as borescopes, endoscopes or videoscopes for the inspection of restricted access areas. A fully registered digital recording system is very convenient for precise analysis and comparisons. Much of the success of visual inspection depends on the surface condition and the lighting arrangements. Remote photography and video, may be used for various applications such as the internal inspection of pipes, pressure vessels or valves.