stop down

stop down (third-person singular simple present stops down, present participle stopping down, simple past and past participle stopped down)

1. (photography) To decrease the aperture of a photographic lens, moving from an f/stop represented by a lower number to an f/stop represented by a higher number.
   • 1982, Marvin J. Rosen, Introduction to photography: a self-directing approach, 2nd ed., →ISBN, p. 71:

     The f/stops are arranged so that as you stop down, each stop allows half the amount of light to pass through as the stop before it did.

   • 2002 Dec. 12, "Images from a blurred world," The Economist (retrieved 3 Apr 2009):

     To get an image with a larger “depth of field”—ie, where more of the distant objects as well as the nearer ones in a scene are in focus—the photographer must “stop down” the aperture of the lens, restricting the amount of light admitted.

• stop up