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Aperture Explained in Simple Terms

What Is Aperture?

Aperture is essentially when your lens opens or closes. It is the mechanism that you can alter to make the hole through your lens smaller or larger.

Aperture Explained

Why is aperture so important?

Aperture is a foundation to photography. Yet, many beginner photographers struggle with the concept of aperture when they are first introduced to it. However, once you start to play around with different aperture settings you start to get a better feel for it.

There are two main reasons why you might typically adjust the aperture:

  • Exposure: To control the exposure.
  • Depth Of Feild (& Bokeh): To change the depth of field (focus), often to add some nice bokeh effects.

Aperture, ISO & Shutter Speed Explained:  3 Ways To Control Exposure

There are three ways you control the exposure of a picture. Each one has to do with how light affects your cameras sensor.

  1. Aperture: Aperture affects the exposure of your photograph. Naturally, The bigger the hole, the more light that can pass through. The larger the hole, the more light can pass through. So the more exposed your picture will be. The same goes for the opposite. The smaller the hole, the less light can pass through.
  2. ISO: ISO is primarily the sensitivity of your sensor. Back in the days of film, it was a property of the film. The higher the ISO, the more sensitive to light. Meaning, it will naturally give you more exposed pictures, holding everything else equal. Usually, you use lower ISO in good light conditions.
  3. Shutter Speed: Shutter speed is how quickly the shutter releases to expose the light to your sensor. The faster the shutter, the less light passes through. The slower the shutter speed, the more light can “burn” into the sensor to create the photographic image.

Aperture Function In Low Light

To give you a better idea of how Aperture will help you as a photographer, say you wanted to take a picture in a dark room.

Dark Room Aperture Function

If you have a small aperture, you essentially have a small hole. (However, the F-stop number will be higher – see below).

What do you think will happen?

Well, not very much light will come through, right?

So if you open the aperture up to make it bigger, more light can pass through. You need that light passing through, in a darker room. So naturally opening the aperture up is 1 of 3 ways to control the exposure of your picture in a dark (or light) environment.

Aperture In Bright Conditions

What if you were outside and there’s already plenty of light? You may need to dial your aperture down (to a smaller hole) so doesn’t let as much light through the opening.

The closing of your aperture is one way that you control the exposure of your pictures.

F-stop Numbers Explained

The thing you need to remember is that aperture has a number associated with it – and this is called an F-stop.

This F-stop number can be confusing to many people because there is an inverse relationship between the F-stop number and the actual aperture size.

This inverse relationship means the smaller the F-stop number; the larger your aperture will be (to let more light in).

So if you have a small f-stop number, your aperture will be bigger. If you have a higher f-stop number, the aperture will be smaller.

If you want more light to come through to your pictures, you need to pick a lower f-stop member.

Conversely, if you want less light to come through (if your images are overexposed), you will want to choose a higher f-stop number (which will make your aperture smaller).

If you look at below the diagram, F1.8 is where the aperture is completely open. this smaller aperture number means it’s open all the way, and it can vary depending on the lens.

f stop explained


For example, some lenses will have a maximum of-of F2 or F1.8, etc.

How To Set Aperture On Your Camera

To change the Aperture on your camera; there are a few ways to do that:

  1. Manual Mode: one way to change aperture is to set your camera to manual. This allows you to set all the settings yourself. Everything from shutter speed to the aperture, to the ISO, need to be manually set in manual mode. Manual mode allows you to adjust the three most important ways that you influence the exposure of your picture. This is ideal for learning and more advanced or professional photographers.
  2. Aperture Priority Mode: the Aperture priority mode is half manual, have automatic. In this mode, you can manually set your aperture (f-stop) number. Then your camera will use it’s built-in light meter to automatically choose the shutter speed and ISO, so you have a correctly exposed picture.

The way you enter aperture priority mode is typically set on the top dial. However, it is slightly different depending on whether you have a Nikon or Canon:

  • Nikon and most other cameras: A
  • Canon: AV

When you’re first starting out it may be a good idea to your camera and Aperture priority vs. Manual mode. For Nikon, you should see an “A” on your dial, or for cannons you should see an “AV” on the dial.

Every time you change the f-stop number in Aperture priority mode your camera’s light sensors read the current lighting conditions and automatically adjust the shutter speed and the ISO based to match your f-stop number.

Aperture For Photography Effects

There are particular effects you get with your photos when you use different f-stop numbers.

For example, you would typically choose a different f-stop number when photographing landscape scenes vs. photographing portraits.

Aperture for portrait photography

Usually, when you get someone’s portrait, you want the background of the subject to have that bokeh effect (blurry background):

Portrait Photo example image With Large Aperture (Smaller F-stop):

Smaller F Stop Portrait Example

Aperture for landscape photography

Whereas, in landscape photography, along with using landscape filters, you want the whole image to be in focus; you typically don’t want any part of the image to be blurry. You don’t want any of the blurriness or bokeh effects like you would in portraiture photography.

Landscape Photo example With Small Aperture (Larger F-stop)

Larger F Stop Landscape Example

F/22 Aperture

The way you get an image that is in focus (no matter how close or far away) is by having a smaller Aperture. A smaller aperture is usually reserved for things like landscape photos and for photographing groups of people. Remember, this means you need a higher f-stop number to get that smaller aperture.

For landscape photos you want a higher f-stop number, whereas if you’re doing portrait work, you typically want that Bokeh effect in the background, so you want to use a lower f-stop number (remember, a lower f-stop number means a larger aperture size).

All this has to do with depth of field. The changes in aperture also change your depth of field. It changes the area that is in focus, depending on how far away or how close up the object is.

Aperture and F-Stops Relationship

Example Of F-stops And Bokeh

  • f/1.8: highest bokeh effect
  • f/2.8: Slightly less bokeh than f/1.8
  • f/4: less bokeh than f/2.8
  • f/5.6: less bokeh than
  • f/8: less bokeh than f/5.6
  • f/11: less bokeh than f/8
  • etc
Jeffrey Bowdoin

Author Jeffrey Bowdoin

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