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PBG: The Exposure Triangle – Understanding Aperture #3

PBG: The Exposure Triangle – Understanding Aperture #3
aperture - the exposure triangle

You may be heard for sure about aperture and you may be one step closer to understanding it.

Understanding Aperture is the third part of a longer series of in-depth post designated for beginner photographers or anyone interested to learn photography.

Aperture. What is Aperture?

aperture on exposure triangle

Aperture, or the F-number, is known in optics to be an opening or a hole through which light travels.

When a complex system like lenses has a mechanism to change the opening size, we technically know that “the aperture changes.”

Larger or wider Apertures

Wider Apertures (e.g. f/1.8) have larger openings and allows more light to come into the camera sensor.

There are prime lenses (you can check this article about prime vs zoom lenses) with large opening better than any zoom lenses, perfect for low light photography or even astrophotography.

Combining long exposures with large apertures at night, you can create outstanding night sky pictures as an instance.

As well, using wider apertures during the day time allows you to freeze the moment. (1/800th of a second, 1/2000th of a second).

With the large aperture, you can create less depth of field, a unique experience of creating images with only the subject in focus.

Therefore, with less depth of field, you can create amazing bokeh also, if there are any source lights in the background.

Aperture is affecting the shutter speed and ISO and is a part of the exposure triangle

But more information about the depth of field bokeh, shutter and ISO will follow on the next posts of this series.

Smaller apertures

Smaller apertures (e.g. f/22) have smaller openings, in order to create longer exposures or for better control of the light.

By letting less light in, you can have better control over lighting on overexposed scenes and more.

Having more control over the F-number, you can also create different unique exposure effects.

Silky waterfall or sea, trail lights, vivid landscapes, all of them and more can be obtained by creating long exposures.

Why is so important controlling the Aperture?

  • Controlling the light
  • Balancing and creating long exposures

In the process of controlling the light, the aperture being part of the exposure triangle is having the absolute main role.

With the ability of a lens to change its Aperture, both manually and automatically, we can have a direct relationship with the shutter and ISO in order to take a properly exposed photograph.

With this simple but complex process, we can control the amount of light coming into the camera sensor.

Increasing the shutter speed by stopping down the aperture with the right ISO values, we may be able to create and balance long exposure photographs.

When to use specific apertures

Larger apertures

  • Night photographs
  • Astrophotography
  • To obtain bokeh
  • For a shallow depth of field

Smaller Apertures

  • Long exposures during day time
  • Soften the water (waterfall, waves)
  • Landscapes (larger depth of field)

Further, I am going to discuss and explore a little the above cases where either larger or smaller apertures are needed.

Night Photography.

Taking photographs during the night handheld can be a bit challenging therefore a tripod may be required.

Depending on the scene and the amount of light present, taking photographs during the night will probably require you to set your Aperture to its maximum (largest), but not always.


Compared to night photography, in Astrophotography or photographing the night sky will definitely require you to have a fast lens with a very large aperture and a tripod of course

Our aim is to let as much light as possible to fall into our camera sensor by right exposing with a minimal noise coming from high ISO values.

To obtain bokeh.

Let’s assume that you may know what bokeh is, if not follow this link (external) for a quick read (What is bokeh)

To be able to take photographs with beautiful bokeh, you may need to met certain conditions.

Some of them are: Darker scenes with light sources in the background (night photography), a fast lens with a large aperture and a subject relatively close to you (to the photographer).

The depth of field is becoming shallower and the background lights are becoming bokeh while the subject or element remains on focus.

It is recommended a darker scene such as photographing during the night for the best bokeh because the source of light from the background intensifies on the dark scene.

This doesn’t mean that is not possible to obtain bokeh during the daytime, it is just not as intense as the night time.

Shallow depth of field is obtained by photographing the subject closer to you with a larger aperture and creating a greater difference in the focal plane in concordance with the focal length of your lens.

Or take a photo to your pet close-up. Whichever version is easier to understand ????

This is working the same way as creating bokeh, only consider a different scene.

Smaller apertures

What about taking long exposures during day time? I wrote a while back a guide into long exposure photography if you want to read it, but how does a smaller aperture help?

When closing down (or stepping down) the aperture, the opening or the hole becomes smaller, even the size of a needle for some lenses. The light will find a hard time getting through that opening, therefore, the shutter has to remain open a longer period of time to properly expose the photograph.

Although this may not be enough to take very long exposures, the ND filters are needed. This stops even more light to come into the camera sensor, and to properly expose a photograph, the shutter may be open even for minutes and more.

When photographing water such as waves, waterfalls, rivers etc, due to the long exposure the image will create a special effect which softens (or smoothing) the waters.

This would be the very main reason a small aperture is very useful during day time.

Please remember that a tripod is needed for all the above scenarios where an aperture is smaller, as the shutter will have to remain open a longer period of time.

In the case of a landscape photograph, it is much recommended to step down your aperture, allowing the depth of field to be larger (tripod needed)

You don’t want that some elements of the landscape photograph to be out of focus due to the difference in the focal plane

The Aperture Priority Mode

Above I was talking about scenarios where a wide or small aperture is needed, but when to use the aperture mode of your camera and what is it in the first place?

The Aperture Priority is a camera mode which allows you to manually set your aperture while the shutter is automatically adjusted for your lighting condition in order to properly expose the photograph. (P)

ISO is also adjusted automatically if this is set on AUTO mode, between the minimum and maximum values your camera is set up (e.g. 100-6400)

When to use the aperture priority mode?

Every photographer would say differently. Me, personally I use in the following cases (but not always):

  • In good lighting scenarios.
  • While doing street or portrait photography
  • When I want to create bokeh or shallow depth of field
  • In the low light condition when you want the aperture to remain open at the widest value your lens can support
  • Any other cases you need a specific f-number.

Sweet&Love my camera! Conclusion:

With honesty, this mode is the main mode I use when taking photographs and is by far my favourite.

Is the simplest, yet a powerful mode, which can make a huge difference in your photographs.

But to know, the aperture should be never ignored and experimented with it.

Thank you for reading our aperture guide, the third post from our PBG series. Stay tuned for more.

PBG: The Exposure Triangle - Understanding Aperture #3

PBG: The Exposure Triangle - Understanding Aperture #3

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Understanding aperture is the first post of the exposure triangle and the third one from our PBG series. Aperture play one of the most important role in photography. Do you want to read more about aperture?