With the 'long shades' the complete change takes place over a distance of about one metre or more. With 'short shades' the change runs over a distance of less than one metre.
See also the TRC Needles entry on shaded threads or cloth.
Source: CLABBURN, Pamela (1976). The Needleworker’s Dictionary, London: Macmillan London Ltd., p. 162.
GVE