Aperture is an important camera setting to consider when photographing anything, and it's especially important when photographing subjects that are close to you or brought close by a telephoto lens with a long focal length. Aperture sets the depth of field, or that band of space that is in focus between the camera and the point furthest from the camera. Aperture is measured in f-stops with lower numbers creating a shallow depth of field and high numbers creating a deeper depth of field. For example, an aperture setting of f/5.6 will produce a narrower depth of field than an aperture setting of f/8.
The aperture of a lens is the hole through which light travels before landing on the sensor. The wider the aperture, the more light will hit the sensor, meaning that aperture can have a significant impact on the shutter speed required for a well-exposed photograph. A narrow aperture (high f-stop number) will require a longer exposure time or a higher ISO setting to compensate.
This is important to remember when you're photographing subjects that are close to you or brought close by a telephoto lens with a long focal length. It's important, that is, if you want the entire subject to be in sharp focus or if you wish to have some of the subject in soft focus. If you look closely at photographs of wildlife like birds or insects, sometimes you'll notice that parts of the subject are in focus and other parts are slightly out of focus. What you're seeing is the depth of field, but you're also seeing some indication of how close a photographer was to their subject, either physically or telephotographically. Obviously, the focal length of the lens comes into play, so that a lens with a very long focal length allows a photographer to stay further away from their subject while maintaining a close shot.
Most of the time, you're probably going to want your entire subject in sharp focus, so paying attention to the aperture setting is important to making sure you have enough depth of field. Recently, I was out photographing birds when a dragonfly landed on some leaves close by. I started to photograph the insect, starting with an aperture of f/5.6 and then increasing it to f/8 to increase the depth of field. The dragonfly flew away before I could try some snaps at even higher aperture values, like f/11 and f/14, but it turns out that f/8 was pretty much the perfect aperture for getting the full body of the dragonfly in focus.
Here are some examples of the dragonfly taken at f/5.6 and f/8 to illustrate the impact of aperture on depth of field for subjects that are close. The depth of field for a close subject is really shallow at f/5.6! This dragonfly was probably 15ft -17ft away and I was shooting with a Canon R5 body and a 600mm f/4 + 1.4x extender (840mm).
Dragonfly at f/5.6 vs f/8
In the two photos below, the focal point is on or very close to the thorax (where the wings attach). In the photo shot at f/5.6, the focus on the abdomen is quite soft, especially where its colour turns from light brown to dark orange. In the photo shot at f/8, the entire abdomen is in sharp focus because the depth of field is deeper.
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| Dragonfly with aperture at f/5.6 |
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The difference in sharpness on the abdomen might appear subtle in these images, but when viewed on a large screen or printed, the difference is quite noticeable, especially as you progress down the abdomen to the tip.
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| Dragonfly Closeup at f/5.6 |
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| Dragonfly Closeup at f/8 |
