Which is the ‘correct’ aperture?
You can choose any aperture, but some f-stops are more naturally suited to certain subjects
Large aperture
The shallow depth of field offered by apertures in the region of f/1.2 to f/4 makes it easier to blur foreground and background details, making them good choices for ‘dreamy’ portraits of people or animals. You’ll need to be spot-on with your focusing, though, as the depth of field will be shallow. Large apertures also suit low-light and action photography, where you need lots of light to enable faster shutter speeds.
Mid-range aperture
Apertures between f/8 and f/11 are typically in the middle of a lens’s range, and they tend to give a reasonable balance of the amount of depth of field and ‘sharp’ shutter speeds. They also usually form the sweet spot of a lens’s optical performance and are more forgiving with focusing errors compared to larger apertures. They’re a good choice for ‘everyday’ photography: “f/8 and be there”, as the saying goes…
Small aperture
When depth of field matters above all else, use f-numbers of f/16 and beyond. Apertures in this range are useful for macro and close-up photography, where depth of field is naturally shallow and every millimetre counts. They are also useful for expansive landscapes, where you need everything from the foreground to the horizon to be recorded in detail. Diffraction can be a problem, though – see over the page.