“…The variation of overall colour or textural characteristics from surface to surface is known as the tonality problem. Any changes in the tonality, however subtle, will still become [113,151,20,37,127,18,129] 3. Joint spatial/spatial-frequency [17,52,38,59,117,144,66,62,132,128,112,152,9,63,6,89,84,119,153 [60,123,131,80,122,39,130,149] significant once the surfaces are placed together.…”