Waterhouse stop
（重定向自Waterhouse diaphragm）
![Two views of an early Dallmeyer Soft Focus Series B with a focal length of 8½](/Images/godic/202502/20/Dallmeyer_waterhouse1410.jpg")
![Cassell's Cyclopedia of Photography 1911 identifies John Waterhouse of Halifax as the inventor in 1858 of Waterhouse stops,](/Images/godic/202502/20/Diaphragms_Cassells_19111410.png")
The Waterhouse stop or Waterhouse diaphragm is an interchangeable diaphragm with an aperture (hole) for controlling the entry of light into a camera. A thin piece of metal (the diaphragm) is drilled with a hole (the aperture); a set of these with varying hole sizes makes up a set of Waterhouse stops, corresponding to what today we call f-stops or f-numbers. Photographic lens makers provided slots in lens barrels for the insertion of the chosen stop.