Abstract: A thermal transfer dyesheet comprising a substrate bearing a region of a thermally transferable dye, the region including a first printable portion within the region having a first optical density, a second printable portion within the region having a second optical density, the difference in optical density between the first and second optical densities being detectable by a detection means on a dyesheet printer, and a third printable portion within the region having an optical density substantially the same as that of the first printable portion is provided, together with a method for manufacture of the dyesheet and an associated printer.