What is maximum aperture and why does it matter? Different lens types compared
The aperture setting of the lens controls the amount of light that passes through, so you can use this setting as part of your exposure adjustments.
In dim light you can use a wider lens aperture so that more of the light gets through to reach the sensor, and in bright light you can use a smaller lens aperture to reduce the intensity.
There are other exposure adjustments too, of course, including the shutter speed, or exposure time, and the ISO, or sensitivity setting of the sensor. In practice you adjust all three – aperture, shutter speed and ISO – according to the conditions and the type of subject you’re shooting.
However, if the lens lets through more light, you can use a faster shutter speed, which means you can freeze fast-moving action more easily, or shoot in lower light without risking camera shake from slow shutter speeds. Without that, your only alternative would be to increase the ISO setting, which increases the digital noise in your pictures.
The lens aperture also has an effect on the depth of field, or near-to-far sharpness in your pictures. The wider the aperture, the shallower the depth of field. For landscape photography and close-ups, extra-wide apertures are less important, because you generally want as much depth of field as you can get. For portraits and sports photography, however, it’s much better if you can blur the background so that your subject stands out more clearly – and that’s where a wide maximum aperture is important.
This is why so-called ‘portrait’ lenses and professional telephotos have wide maximum apertures. They are more expensive, but they give the special shallow depth of field effects that professionals look for.
Lenses with a wide maximum aperture let you capture atmospheric portraits, sports and low-light shots without the need for a tripod, flash or higher ISOs