The number of dimensions given when specifying an NDF section need not necessarily correspond with the actual number of NDF dimensions, although usually it will do so.
If fewer dimensions are specified than there are NDF dimensions, then any unspecified bounds will be set to (1:1) for the purposes of identifying the pixels to which the section should refer. Conversely, if extra dimensions are given, then the shape of the NDF will be padded with extra bounds set to (1:1) in order to match the number of dimensions. In all cases, the resulting section will have the number of dimensions actually specified, the padding serving only to identify the pixels to which the section should refer.
This process corresponds exactly to that which takes place via the
programming interface when NDF_SECT is called (see
§).