Diaphragm (optics) bright spots, for example night cityscapes. Some cameras, such as the Olympus XA or lenses such as the MC Zenitar-ME1, however, use a two-bladed diaphragm with right-angle blades creating a square aperture. Similarly, out-of-focus points of light (circles of confusion) appear as polygons with the same number of sides as the aperture has blades. If the blurred light is circular, then it can be inferred that the aperture is either round or the image was shot "wide-open" (with the blades recessed into the sides of the lens, allowing the interior edge of the lens barrel to effectively become the iris).
Diaphragm (birth control) the diaphragm. Insufficient studies have been conducted to determine effectiveness without spermicide. It is widely taught that additional spermicide must be placed in the vagina if intercourse occurs more than six hours after insertion. However, there has been very little research on how long spermicide remains active within the diaphragm. One study found that spermicidal jelly and creme used in a diaphragm retained its full spermicidal activity for twelve hours after placement of the diaphragm. It has long been recommended that the diaphragm be left in place for at least six or eight hours after intercourse. No studies have been