Section 11(6)(c) in The Merchant Shipping (Crew Accommodation) Rules, 1960
(c)The points at which illumination shall be measured shall be as follows :-(i)where a general measurement points are prescribed for the illumination of a space, then measurements shall be taken at every point midway between every 2 adjacent lamps and at every point midway between every lamp and any position on any boundary of this space. Provided always that where within any space a part of that space (being a part of that space available for fee movement) is shaded from the direct rays of a lamp by a re-entrant angle formed in the boundary of the space, then the central point of the part of space so shaded shall also be general measurement point; and(ii)where particular measurement points are also prescribed for a space, then measurements shall in addition be taken at every such point.