For those who shoot with antique lenses but are missing Waterhouse stops, photographer Markus Hofstätter has put together a tutorial that shows a couple of ways that shooters can create their own. Older vintage lenses, such as Petzval ones, that don’t have an iris diaphragm instead use a set of what are called Waterhouse stops instead. Named after 19th-century astronomer and photographer John Waterhouse, the component has a set aperture that controls the entry of light into a camera in the same manner that modern-day lenses do with a built-in iris diaphragm that has blades. The difference is that Waterhouse stops are manually inserted in slots in the lens barrel.