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Explaining F-Stops - What it is and How To Use it in Your Photography

This is a post that is continuing the line of fundamental photography lessons started in our Lighting basics tutorial. Give that a check out after reading this one!

Aperture is one of the most important aspects of any camera setup. Aperture, along with ISO and your Shutter Speed, is the largest dictator on how exposed your shot will be, and how you set up the rest of the set if that is the environment you find yourselves in.

But what is aperture exactly?

What is an F stop?

The F-stop of your lens determines how much light is let into the camera sensor. It describes how far the shutter will open in the actual lens! An F-stop is describing how much light the physical blades inside your camera will allow into your camera's sensor.

Camera Lens Showing Blades, Explaining F-Stop
The Blades Within a Lens, Dictating the F-Stop

When deciding on what F-stop to use for your image, it is important to know what the relationship between this number and the outcome of the image will be. The lower the F-stop, the higher amount of light will be exposed onto the sensor of your camera.

How Aperture Affects Exposure

As we've seen, the smaller the aperture, the less light gets into the camera. This means that this setting will invariably decrease the exposure of any shot that you are taking!

Setting your Aperture will be decided not only on the artistic intent of your shot (adding more bokeh, more on later, or a crisp shot for nature/landscape) but also the ‘exposure triangle'. This is the relationship between the three deciding factors of exposure - Aperture, ISO and Shutter Speed.

Diagram of the Exposure Triangle for Photography
The Exposure Triangle

If your Aperture is too wide (a lower F-stop), then your image could end up overexposed.

Photo of a Woman in an Overexposed Image
An Overexposed Image

If your Aperture is too closed (a higher F-stop), then you could end up with an underexposed shot.

Landscape Photo at Frensham Ponds Showcasing an Underexposed Image
An Underexposed Shot

How Aperture Affects Bokeh / Depth of Field

One of the keys determining factors when selecting your F-stop for any project/shoot is the bokeh effect (the depth of field on a photo). This is the blurriness that you see behind a focused subject when a photo is taken at a small F-stop (generally F2.0 and below).

Portrait Image of Women in London
See The Background Afffected by the Bokeh (Blurriness)

This can be seen on smartphones with the portrait setting.

A wide depth of field (higher F-stop number) is key to keeping more of your frame in focus, especially useful for nature photography for example, and a low depth of field (lower F-stop number) is key for portrait photography etc.

Image of people in rowboats on a lake within a mountain range in and idylic setting
A Higher F-Stop (4 and above) is Required to Achieve Results in Landscape Photography

So What Should I Use?

The Aperture setting that you use is all decided on what you want to achieve with your photography, as you can adjust the other settings in your camera to compensate for any exposure problems.

And don’t be afraid to play around with exposure! A traditionally seen ‘underexposed’ shot may be what style / impression that you are going for, and that is fine! Play around, see what works for you and don’t be afraid to get a ‘bad shot’!

In the next month, I’ll be releasing the next two posts in this line of photography fundamentals, looking at ISO and Shutter Speed. Keep an eye out for these and let me know what you want out of the next line of camera lessons!

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