The Magic Of Camera Zoom: Capturing Far-Away Objects

Focusing is a crucial technique in photography, ensuring that the desired subject is in focus and not blurry. The process of focusing involves adjusting the lens to direct light rays onto a specific point, known as the plane of focus, to create a sharp image. This is particularly important when capturing fast-moving subjects, such as birds in flight, or in low-light conditions. One term related to focusing in photography is depth of field, which refers to the range of distances within a photo that appear sharp. When focusing on far-away objects, photographers may utilise a technique called racking focus, where the area of sharp focus shifts from one plane to another during the shot, bringing distant objects into view.

Autofocus vs Manual Focus

Autofocus (AF) and manual focus (MF) are two methods of achieving a clear shot with your camera. Autofocus is when the camera sets the focal point, while manual focus lets the photographer determine the focal point.

Autofocus

Autofocus is generally faster than manual focus, although its speed depends on the camera and lens type. Sports-oriented equipment, for example, is designed to be much faster. Autofocus has also seen advancements such as tracking, which enable the camera to lock focus on a subject and follow it through the frame. This feature is particularly useful for capturing moving subjects.

Autofocus systems rely on contrast to identify objects, so they struggle in low-contrast scenes, such as those with heavy backlight. They also depend on light to function, so they perform poorly in low-light conditions. Autofocus can also be confused by scenes with many objects, as they tend to focus on foreground objects. They are also not very precise, so while they can get you close to your desired focal point, they may not be able to focus exactly where you want them to.

Manual Focus

Manual focus gives the photographer greater creative control, as they can determine the exact focus point. This method is ideal for situations where autofocus may struggle, such as in low light conditions, when shooting through glass or fences, or when there are many objects in the scene. It is also more precise, allowing the photographer to carefully pick the point of focus from a chaotic scene.

However, manual focus is generally slower than autofocus, making it less suitable for capturing moving objects. It also requires the photographer to choose the point of focus, which can be challenging in certain situations, such as when shooting from the hip.

When to Use Autofocus

Autofocus is generally recommended as the default option, especially when photographing wildlife on the move, birds in flight, street photography, or pets at play.

When to Use Manual Focus

Manual focus is best used in specific scenarios where autofocus struggles. This includes macro photography, deep landscape photography, complex focus bracketing, scenes with many distracting foreground elements, and situations where you need to nail a precise point of focus, such as portrait photography. It is also ideal for nightscapes or any scenes with low light, as well as situations where you know where your subject will be in advance, such as a bird flying to the same perch.

Zoom Lenses

The convenience of variable focal length comes at the cost of increased complexity, weight, dimensions, and a potential compromise on image quality, autofocus performance, and cost. All zoom lenses suffer from at least a slight loss of image resolution at their maximum aperture, especially at the extremes of their focal length range. This effect is particularly noticeable in the corners of the image when displayed in a large format or high resolution. The greater the range of focal lengths offered by a zoom lens, the more these issues are likely to be exaggerated.

Some examples of zoom lenses include the Sony FE 200-600mm f/5.6-6.3 G Master OSS, which is great for astrophotography due to its large focal length, and the Nikon Z 70-200mm f/2.8 S, which offers excellent image quality and optical image stabilization. Other options include the Canon RF 28-70mm f/2L USM, which produces high-quality images but comes with a high price tag, and the Sigma 70-200mm f/2.8 DG OS HSM, which offers similar performance to more expensive lenses at a more affordable price point.

Aperture

The size of the aperture is measured in f-stops, with smaller f-stops like f/1.8 representing a wide opening, and larger f-stops like f/22 indicating a narrow one. Lower f-stops result in more exposure, as they represent larger apertures, while higher f-stops produce less exposure due to their smaller size. This relationship may seem counterintuitive at first, but it becomes clearer through experimentation with different f-stops.

In addition to its impact on depth of field, aperture also affects shutter speed. A lower f-stop, or larger aperture, allows more light to enter the lens, enabling a faster shutter speed. Conversely, a higher f-stop and smaller aperture reduce the amount of incoming light, necessitating a slower shutter speed to achieve proper exposure.

Moreover, aperture contributes to the bokeh effect, which refers to the aesthetic quality of the background blur in an image. A wide aperture produces pleasing bokeh, making it a popular choice for portrait photography to achieve a soft, unfocused background.

In summary, aperture is a fundamental concept in photography that governs various aspects of an image, including depth of field, shutter speed, exposure, and bokeh. By adjusting the aperture, photographers can creatively manipulate the amount of light entering the camera, influencing the final image's overall appearance and mood.

Depth of Field

The term "depth of field" (DoF) refers to the distance between the closest and farthest objects in a photo that appears acceptably sharp. In other words, it is the area in front of and behind the subject that is in focus.

By adjusting these factors, photographers can control the depth of field to achieve the desired effect. For example, a shallow depth of field can be used to highlight a specific subject or create a soft, blurred background. On the other hand, a large depth of field is often used in landscape photography to keep most of the scene in focus.

Understanding depth of field is crucial for photographers to master as it provides artistic freedom and allows them to create the images they envision.

Focal Length

For example, a 500mm lens has a longer focal length than a 50mm lens, and will therefore produce images that are more "zoomed in". In practice, photographers use different focal lengths to capture different types of images. Wildlife photographers, for instance, tend to use longer focal lengths to get closer to their subjects without being seen, whereas landscape photographers typically use shorter focal lengths to capture wide vistas.

There are two types of lenses: prime and zoom. Prime lenses have a fixed focal length, whereas zoom lenses have variable focal lengths. Zoom lenses are more versatile and convenient as they allow photographers to access multiple focal lengths without needing to change lenses. However, prime lenses tend to be more compact and lightweight, sharper, with larger maximum apertures that perform better in low-light conditions.

Frequently asked questions