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).
The Eye in the Door The Eye in the Door The Eye in the Door is a novel by Pat Barker, first published in 1993, and forming the second part of the "Regeneration" trilogy. "The Eye in the Door" is set in London, beginning in mid-April, 1918, and continues the interwoven stories of Dr William Rivers, Billy Prior, and Siegfried Sassoon begun in "Regeneration". It ends some time before the conclusion of the First World War later the same year. The third part of the trilogy, "The Ghost Road", continues the story. Whereas "Regeneration" is an anomalous, but not unique, mixture of fact and fiction,