Dark field, front light illumination
In dark field, front light illumination, reflected light is not collected by the optics. In this way, only scattered light is captured, enhancing the non-planar features of the surface as brighter characteristics on a dark background (the dark field - see Fig. 11 and 13.a - 13.b ).
Again, this effect is commonly reproduced by means of low angle ringlights (Fig. 12).
