“…Nevertheless, one particular among them, the so-called universal (k, k)-space, (R 3 , f kk ), captures the essence of all digital surfaces for the pair (k, k). More precisely, the main result in [5] states that any digital surface in a (k, k)-space is also a digital surface in (R 3 , f kk ). Next we recall the definition of the lighting functions f kk and some immediate properties.…”