English: Heckler & Koch rotating drum sight line pictures. The red help lines denote how to correctly center the front post.
Left; V-notch and hooded front post aligned for rapid target acquisition, close range, low light and impaired visibility use.
Right; aperture and hooded front post aligned for a user selectable range setting on battle rifles or assault rifles.
The rotating drum sight apertures on Heckler & Koch sub machine guns have various diameter apertures to optimize the sight line for various ambient light conditions instead of ranges.
The theory of operation behind the aperture sight is often stated that the human eye will automatically center the front sight when looking through the rear aperture, thus ensuring accuracy. An additional benefit to aperture sights is that smaller apertures provide greater depth of field, making the target less blurry when focusing on the front sight.
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