APER­TURE EX­PLAINED

What is max­i­mum aper­ture and why does it mat­ter? Dif­fer­ent lens types com­pared

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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.

Creative con­trol

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

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