Waterhouse stops were also used in photographic enlargers in the darkroom. Photographic lenses also include those used in enlargers and projectors. Many Wray lenses remain in use, especially in photographic enlargers. The EL-Nikkor series of lenses are designed for photographic enlargers. The reason was that commercial processors used MINOX enlargers. The company manufactured photographic enlargers and other photographic equipment throughout the 20th century. Such adjustments are used for darkness and color adjustment in photographic enlargers, for example. The firm specialized in manufacturing low priced photographic enlargers. Zenit manufactured a large range of enlargers as well. Durst have filed over 500 patents for various components and designs of enlargers. These enlargers can also be used with variable-contrast monochrome papers. The other Sun Ray enlargers are focused through a bellows (photography). Omega is the name of various medium-format cameras and enlargers. None of Sun Ray's enlargers are equipped with autofocus. Some enlargers, such as Leica's "Autofocus" enlargers, perform this automatically.