Charts of this type combine the large, unbroken areas that are characteristic of Opacity Charts, with the striped design of a Display Chart. The larger areas permit wide aperture photometric measurements and visual colour comparisons, while the striped area is uniquely effective for hiding power comparison and display. Spreading Rate Charts (Forms12H and 13H) are accurately 0.1 square meters (approximately one square foot) in area, and are designed for brushout application at specified spreading rates.