Aperture
The adjustable opening in a camera lens that controls how much light reaches the sensor, measured in f-stops.
Aperture values follow a counter-intuitive scale: smaller f-numbers (f/1.4, f/2) indicate wider openings that admit more light, while larger f-numbers (f/11, f/16) indicate narrower openings. Each full f-stop doubles or halves the light entering the lens. Beyond exposure control, aperture directly affects depth of field — wide apertures create shallow focus ideal for portraits, while narrow apertures produce deep focus ideal for landscapes. Maximum aperture is a key lens specification that determines low-light capability and background blur potential. Fast lenses with wide maximum apertures like f/1.4 or f/1.8 are prized for their versatility in challenging lighting conditions and their ability to produce pronounced subject separation.