Minimum, Optimum, and Maximum Apertures
@soskha
Every lens has its limits; it will have a maximum f/stop – the largest its aperture will go – which
we call wide open. The maximum aperture is noted in the name of a lens: “Nikon 50mm f/1.8”, for
instance, or “Canon 200mm f/4”. On a zoom lens, this is often a range: “Pentax 18-55mm f/3.55.6”, where the maximum aperture is f/3.5 at 18mm and closes down to f/5.6 when zoomed to
55mm. Less advertised are the lens' minimum apertures. They are often f/22 or f/32; only very
specialized lenses will shrink down to f/64, or to Ansel Adams' mythical f/90! Every lens, too, has
an optimum aperture. This is different for every lens, even different units of the same model. It is
the aperture at which the lens achieves its sharpest focus at its center point; the point where all
the lens elements line up as perfectly as possible, with no distortion. It is usually found around f/8,
but can fall anywhere, depending on the lens design, and on chaos theory.
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