The following example shows how to calculate the relative aperture (f number) of a pinhole camera: If the pinhole diameter is 0.5 cm and the distance between the pinhole and the film is 75 cm, we divide 75 by 0.5 to get a relative aperture of f-150.
現舉一例來看針孔相機光圈如何換算：若針孔直徑為 0.5 公分，而針孔與底片的距離為 75 公分，以 75 公分除 0.5 公分可換算出 f150 的光圈值。