Understanding Camera Focus And The Beauty Of Blur

There are many reasons why a photo may be blurry, and it's important to identify the cause to avoid making the same mistake twice. One of the main reasons for blurry pictures is poor focusing, which can be caused by camera movement, subject movement, missed focus, insufficient depth of field, or lens softness. Another reason could be the use of extremely high ISO settings, which can cause an image to blur. To fix this, photographers need to adjust the depth of field, which refers to how much of the picture is in focus. This can be done by moving the camera farther away from the subject, using a lens with a smaller focal length, or setting a narrower aperture.

Camera movement

Moving Camera

When the camera is in motion, even a slight movement while the shutter is open can cause the whole photo to become blurry. This is known as "camera shake blur". The slower the shutter speed, the more likely it is that camera movement will cause blurring. Using a tripod can help to avoid this, as it keeps the camera steady. Alternatively, image stabilisation technology can help to counter the effects of a moving camera, but it is not a substitute for a tripod.

Moving Subject

When photographing a moving subject, the speed of its movement relative to the shutter speed will determine whether the subject appears sharp or blurred in the photo. This is known as "motion blur". A faster shutter speed can freeze the motion and make the subject appear sharp. However, if the subject is moving very fast, even a quick shutter speed may not be sufficient to prevent motion blur.

Camera and Subject Movement

In some cases, both the camera and the subject may be in motion, which can result in a blurring effect in the photo. This combination of camera shake and motion blur can be particularly challenging to manage and may require a very fast shutter speed or the use of a tripod to capture sharp images.

Subject movement

If you are shooting a fast-moving subject, such as a cyclist, you will need a shutter speed of at least 1/500th of a second to freeze the action. For slower-moving subjects, such as a person walking or a slow-moving stream, you will need a much slower shutter speed, closer to half a second, a full second, or longer, to capture the motion as a blur.

When shooting fast-moving subjects, it is important to use continuous or servo focus mode, which will allow your camera to continue adjusting its focus while you track the moving object. Additionally, using a telephoto lens may require a faster shutter speed since camera shake is more pronounced with longer focal lengths.

To capture motion blur effectively, you can use a technique called panning, which involves moving the camera parallel to the movement of your subject. This will result in a still subject and a blurred background. When panning, it is important to move the camera as fluidly and steadily as possible and use a shutter speed between 1/15 and 1/60 of a second, depending on the speed of your subject.

By understanding the relationship between shutter speed and subject movement, you can effectively control and utilize motion blur to create dynamic and eye-catching images.

Missed focus

To avoid missing the focus, it is important to learn how to manage the autofocus (AF) settings on your camera. This involves more than just knowing what the AF settings do; you need to be able to choose the right setting for the type of photos you want to take. The best setting often depends on the subject of your photograph. Practice is key—the more you practice focusing, the better you will become at it. Relying solely on the camera to adjust settings may still result in blurry photos because the camera does not know what the main subject of the composition is.

When using autofocus, the camera will often pick out the subject and focus on it. However, sometimes it will set the focus point on another part of the composition, resulting in the main subject being blurry. This can be avoided by using single-point autofocus selection, which allows you to manually set the focus point on the most important part of the composition. While this method is more difficult to get used to and slower to use, it gives you more precision and control over the focus of your image.

Additionally, understanding the depth of field is crucial in avoiding missed focus. The depth of field refers to the amount of the image that is in acceptably sharp focus. It is governed by the aperture setting and other variables, such as the distance to the subject and the focal length. A shallow depth of field, often used in portraiture, means that much of the photo can be blurry, while a narrow aperture setting (indicated by a higher f-stop number) will result in more of the photo appearing acceptably sharp.

In summary, to avoid missed focus, it is essential to familiarise yourself with your camera's autofocus settings and practice focusing on your desired subject. Utilising single-point autofocus selection and understanding the depth of field will also help ensure that your images are sharp and in focus.

Insufficient depth of field

There are a few factors that affect the depth of field. These include the focal length, distance to the subject, the acceptable circle of confusion size, and aperture. A wider aperture setting means you have a shallower depth of field, while a narrower aperture means more of your photo appears acceptably sharp.

In the context of landscape photography, if part of an image is in focus but the foreground or background is out of focus, it could be due to insufficient depth of field. This can be addressed by using a smaller aperture, focusing at the right distance, or capturing multiple images with different focus distances and combining them in post-processing, a technique known as focus stacking.

In macro photography, depth of field depends primarily on aperture value and magnification. Higher magnification ratios result in shallower depth of field, requiring more precise focus to capture sharp details.

Lens softness

Soft focus has been described as "an image that is in focus but has a halo of out-of-focus images around it." The first deliberate use of undercorrected spherical aberration, resulting in halos around highlights (also known as "pearly" highlights), is thought to have been by French pictorialists around 1900. The soft focus effect is used primarily in glamour photography because it eliminates blemishes. In general, soft-focus photography produces a misty, dream-like image, sometimes characterized as romantic.

There is a definable, technical difference between terms like "soft" and "mushy" as they're applied to lenses. "Soft" isn't always bad, and some diffusion or mist filters cause some degree of softening. Softness contributes to the nice rendering of skin, although, to be frank, it can only really do that by removing the resolution that reveals unflattering details.

Frequently asked questions