Samenvatting
An improvement in the double image determination method as in British Standard BS 857 and in the draft of the ISO/DIS 3538 is described. Although the proposed method is of enhanced accuracy and able to provide a photographic result, it can also readily be used in tests of the "go-no go" type. The means of measuring, if required, the Value of the correction to be applied in order to allow for observations made at relatively short distance is also given.