In Part 3 of Exposing The Triangle: The Exposure Triangle for Beginners, we went over the basics of the shutter speed; what it is, the different elements and how they impact proper exposure. In this lesson, we are going to cover Aperture and its impact on the overall process.
What is Aperture?
Camera aperture refers to the opening in the lens that allows light to pass through and reach the camera's image sensor. It is usually expressed in terms of f-stops, which represent the ratio of the focal length of the lens to the diameter of the aperture. A smaller aperture (larger f-stop number) will result in less light entering the camera, which leads to a greater depth of field, whereas a larger aperture (smaller f-stop number) will let in more light and create a shallower depth of field with a blurred background.
Measuring Aperture
Aperture values are measured in f-stops or focal-ratio. The focal ratio is the ratio of the focal length of the lens to the diameter of the aperture opening. It is used to describe the size of the aperture opening in relation to the lens, and is expressed as a numerical value such as f/1.4, f/2.8, f/4, f/5.6, etc.
Bokeh
One desirable effect of using a smaller aperture lens (f1.4, f1.8, f2.8) is bokeh. Bokeh refers to the quality and aesthetic of the out-of-focus areas in a photograph, typically in the background of the subject. It is often characterized by a soft, blurred effect that can create a sense of depth and separation between the subject and background.
How does Aperture impact exposure?
Just like with shutter speed and ISO, you need to accurately balance aperture to achieve proper exposure. Different aperture values will create different "looks" to an image. As stated above, a larger aperture will create a more shallow depth of field in an image, whereas a smaller aperture will create more depth.
Portrait Photography - Most portrait photographers will opt for a larger aperture lens (lower f-stop) to help create a more shallow depth of field aka bokeh. Bokeh is commonly used in portrait photography to separate the subject from the background and create a more pleasing and professional look. When using a larger aperture lens (lower f-stop), more light enters the lens. The photographer will need to adjust shutter and ISO values so that the image is not over exposed or "blown out". This is done by increasing the shutter speed and decreasing ISO.
Landscape Photography - A deeper depth of field (smaller aperture, larger f-stop number) is useful in situations where the photographer wants to capture a scene with a lot of detail, or when the subject and background are both important elements of the photograph. For example, in landscape photography, a smaller aperture is often used to keep the foreground, middle ground, and background in focus. Similarly, in architecture or cityscape photography, a smaller aperture can be used to keep the entire scene in focus. The photographer will need to adjust shutter and ISO values to compensate for the lack of light reaching the sensor. Shutter speed would need to be decreased and ISO increased. In low light situations, the photographer would need to use a tripod to prevent motion blur as a result of slow shutter speeds (under 1/60 sec).
How Aperture impacts Lens Cost and Choice
Low f-stop lenses, also known as "fast" lenses, are often more expensive than lenses with higher f-stop numbers because they require larger glass elements and more complex optical designs to achieve the wider aperture. They are more expensive to produce and take into account factors such as distortion, aberration, and vignetting. Additionally, low f-stop lenses are often preferred by professional photographers and enthusiasts who value their ability to create a shallower depth of field and achieve better low-light performance. As a result, manufacturers may charge a premium for these lenses to reflect their higher quality and performance capabilities.
In the world of lenses there are two types; Prime and Zoom. Prime lenses have a fixed focal length and Zoom lenses have a range of focal lengths. Prime lenses are typically described as "Fast" or having a larger aperture (smaller f-stop). This makes them ideal for portrait and low light photography. Zoom lenses, because of their construction and design, are typically "Slower"(smaller aperture, larger f-stop) than most Prime lenses.
How to change your Camera's Aperture
Unlike ISO and shutter speed, when changing your aperture settings, you are technically changing a setting on your lens and not your camera. But, in some instances, the only way to change aperture is done through your camera. Here are some ways to change aperture, depending on your camera:
A dedicated wheel or dial on your camera.
A control ring on your lens.
Conclusion
In conclusion, understanding aperture is a crucial step in mastering the exposure triangle and achieving proper exposure in your photography. By adjusting the size of the aperture, you can control the amount of light that enters the camera, affecting the depth of field and creating different aesthetic effects like bokeh. When choosing a lens, the aperture should be a key consideration as it will impact the lens's cost and capabilities. Portrait and low light photography typically require a wider aperture (lower f-stop number) to achieve a shallow depth of field and create bokeh. Landscape and architectural photography, on the other hand, often require a smaller aperture (higher f-stop number) to keep the entire scene in focus. Finally, changing your camera's aperture can be done through a dedicated wheel or dial on your camera or a control ring on your lens. Mastering aperture control is an essential skill for any photographer looking to take their craft to the next level.
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