The most common use case for large apertures on a wide angle lens is in low light, especially wide angle views of the night sky.The most common use case for large apertures on a wide angle lens is in low light, especially wide angle views of the night sky. Because of the Earth's rotation and the apparent motion of the sky, shutter speeds need to be limited to about 600 seconds/(focal length in millimeters x crop factor). Higher ISO settings and the resultant lower exposure values tend to generate noise that is just as bright as many dimmer stars, and thus any applied noise reduction can also "eat" stars. Since depth of field is not an issue with celestial objects that are at infinity focus, wider apertures allow lower ISO settings than would be the case with typical apertures used for landscape scenes. Higher ISO settings
In general, even when shooting landscape scenes in low light the preferred method is to use a tripod that allows for longer exposures of static scenes. Even if there are elements moving in and out of the resultant lowerscene using narrower apertures and the resulting longer shutter speeds allow any unwanted elements that move fairly quickly through the scene to not show up in a long exposure values tend.
When shooting large groups with wide angle lenses the narrower aperture is also usually desired to generate noiseinsure that everyone in the photo from front to back is just as bright as many dimmer stars,in focus. If the group is fairly equidistant from the camera and thus any applied noise reductionthe background is "busy" a narrower aperture can also "eat" starsbe used to separate the background from the subjects but care must be taken that focus is accurate and the depth of field is centered on the group.