Visual Inspection is the use of the eye to conduct an inspection. Some say that all inspection is, at the heart, a visual inspection. Methods such as Magnetic Particle or Liquid Dye Penetrant are methods that directly use the eye to determine the presence of a discontinuity by increasing the contrast between the inspection surface and the defect.
Visual Inspection should be performed prior to each application of another inspection method to determine, partially, if the inspection should continue. For instance, if, following a visual inspection, a crack on the surface is found, there isn’t much point in applying ultrasonic shear wave.