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) woman may be fitted with a larger size diaphragm when she is near ovulation. The correct size for a woman is the largest size that she can wear comfortably throughout her cycle. In the United States, diaphragms are available by prescription only. Many other countries do not require prescriptions. The spring in the rim of the diaphragm forms a seal against the vaginal walls. The diaphragm covers the cervix, and physically prevents sperm from entering the uterus through the os. Traditionally, the diaphragm has been used with spermicide, and it is widely believed the spermicide significantly increases the effectiveness of