Using F-Stops In Photography

For photographers knowing how to use f-stops in aperture and manual mode settings is vitally important.

Learning the basics of the exposure triangle will provide a major step forward in your photography skills and knowledge.

There are three parts to the exposure triangle – the aperture, shutter speed and ISO (Sensitivity to light).

The Exposure Triangle

The f-stop is part of the aperture settings and is vitally important for the composition of your image.

F-stop is a term used to denote aperture measurement on your camera and has two main functions:-

1. The aperture controls the amount of light that enters the camera lens which is measured in f-stops.

2. The aperture (f-stops) will also help to establish the look and feel of your image by determining the “depth of field” and will assist the style and look of your final photo.

The diameter of the aperture determines how much light gets through and thus how bright your exposure will be.

Remember, the smaller the f-number – the larger the aperture. Adversely, the larger the f-number – the smaller the aperture.

F-stop chart

The Aperture priority shooting mode, also known Av allows you to set your own aperture and then automatically adjusts shutter speed and ISO to give you a proper exposure.

There is no single f-stop you should shoot with for any given scene.

The best way to learn is to experiment. You will then be able to enjoy the freedom of shooting in manual mode which many top photographers advocate.

Tip: If your not confident shooting in manual mode, mainly use the aperture priority mode (A) on your camera.

Maximum aperture exposure

Depending on your preference, this image was taken at f/20 and has a wider depth of field. There is more detail in the background.

Minimum aperture exposure

Minimum Aperture Exposure – f/4

This particular image was taken with an exposure setting of f/4. The image has less depth of field and the subject stands out more.

Step 1 – Determine aperture settings

Whilst composing your image in camera determine your aperture settings before taking the image. 1 – How much light do I need in the image? and 2 – What depth of field would be best – shallow or wide? There are no rights or wrongs here.

Determine your aperture settings

Step 2 – Set camera settings

Whether shooting your image from a tripod or handheld, set your camera settings to aperture (A) mode or for the more experienced manual mode (M). Many photographers will use the live view screen for this process. Alternatively, the viewfinder can be used as well.

The f-stop chart

Step 3 – Choosing the f-stop

Determine your lighting conditions. Is my composition too dark or too light? Do I need more or less light coming through the lens? Remember, the smaller the f-stop – f/4, f/5 etc – the larger the aperture. Adversely, the larger the f-stop f/16, f/20 etc – the smaller the aperture.

Step 4 – Depth of field

Working in unison with the amount of light required, now determine your depth of field. The smaller the f-stop – f/4, f/5 etc – the less depth of field – “Bokeh” (What is Bokeh?). Adversely, the larger the f-stop f/16, f/20 etc – the more depth of field in your image.

Image taken at f/4 – A shallow depth of field

Step 5 – Other settings

Whether your shooting in aperture or manual modes always keep an eye on your other settings as part of the exposure triangle. Working in unison with f-stop aperture mode, the ISO (sensitivity to light) should be kept as low as possible. Use trial and error at this stage.

Camera settings for the exposure triangle

Step 6 – The final image

Your image should now have the correct depth of field. It is easier getting the correct depth of field in camera rather than making changes in post production. Shooting in Aperture mode – you may have to make adjustments. In manual mode you control all three components within the Exposure triangle.