ASNT Level III- Visual & Optical Testing

Most observers yield only a slight response to ultraviolet radiation at the
nearly visible wavelengths because the lens of the eye absorbs nearly all of it.
Typically, human observers have a response that under normal lighting
conditions extends from 380 to 770 manometers but some individuals have
greater sensitivity at the blue and/or red ends of this range. Of course, at
lower lighting levels even the average observer experiences a shift of the
visible spectrum to shorter wavelengths and vice versa at higher lighting
levels. The spectral range of visible response is therefore not static but
greatly dependent on the lighting conditions.
Charlie Chong/ Fion Zhang