The reason why the role and function of the OHPs have not been taken over by
digital technologies is that OHP offers a more flexible opportunity for involving
students in placing traces of their linguistic performance on the projecting surface
spontaneously and you do not need extremely expensive and sophisticated
equipment. A further advantage of the good old OHP is that there is no other
technology that would let you exploit the educational potential of the so called
shading technique when the silhouettes of various objects placed on the projecting
surface can encourage students guess, predict, describe the vision, i.e. verbalise
their thoughts.