Strictly Necessary Cookie should be enabled at all times so that we hayat save your preferences for cookie settings. 知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 Nominal size of aperture - The nominal aperture size determines the wire spacing. There is a nominal aperture size on each side of the rectangle. According to the https://500px.com/p/shawxajsvenstrup