The Camera's Obsession With Whiteboards: Why The Focus?

There are several reasons why a camera may keep focusing on boards. One reason could be the autofocus feature, which continuously readjusts the lens as the subject moves, causing the camera to go in and out of focus. Additionally, a dirty lens can interfere with autofocus, leading to poor focus. Another factor could be the lighting conditions; as the lighting changes throughout the day, the camera's iris opens to let in more light, affecting the depth of view and causing the image to blur. Furthermore, the tracking auto-focus feature, when enabled, locks the focus on a single subject for a few seconds, which may give the impression that the camera is not focusing on the entire scene. Adjusting settings such as autofocus, tracking auto-focus, and iris mode can help address these issues and improve the camera's focus.

Camera autofocus settings

Understanding Autofocus:

Autofocus (AF) is a feature in modern cameras that automatically adjusts the lens to focus on your subject, ensuring your photos are sharp. There are two types of AF systems: Active AF and Passive AF. Active AF works by emitting a red beam to calculate the distance to the subject and adjust the focus accordingly. Passive AF, on the other hand, uses Phase Detection or Contrast Detection methods to detect contrast and adjust focus.

Factors Affecting Autofocus Performance:

The success of autofocus depends on several factors, including light levels, subject contrast, and camera or subject motion. Autofocus works by detecting areas of high contrast, so ensure your subject has distinct features or textures to help the camera focus accurately. Additionally, the number and type of autofocus points available on your camera play a significant role. High-end SLR cameras may have 45 or more autofocus points, while basic models may only have a single central AF point.

Choosing the Right Autofocus Mode:

Cameras typically offer different autofocus modes suitable for various scenarios. The most common modes are Single AF (AF-S) and Continuous AF (AF-C). Single AF is ideal for stationary subjects as it locks focus on a single point. Continuous AF, on the other hand, is designed for moving subjects. It continuously adjusts focus, predicting the subject's future position to ensure sharp images. Canon calls this "AI Servo," while Nikon refers to it as "continuous" focusing.

Improving Autofocus Performance:

To improve autofocus performance, especially in low-light conditions or when photographing moving subjects, consider the following:

• Use the center focus point, as it is typically the most sensitive and accurate.
• Look for areas of high contrast within your frame to help the camera achieve focus.
• Pre-focus your camera at the anticipated distance of a moving subject to reduce focus hunting.
• For portraits, focus on the eye as it has good contrast and is a standard focal point.
• When shooting in low light, consider using the AF-assist beam, which illuminates the subject to aid autofocus.

Mastering autofocus settings can be challenging, but with practice and an understanding of how your camera's autofocus system works, you'll be able to capture sharp and focused images consistently.

Lighting and background

When a camera repeatedly goes in and out of focus, it is usually due to the autofocus feature. As a subject moves, autofocus continuously adjusts the lens until it is in focus. Depending on the movement, lighting, and background, cameras can sometimes struggle to stabilise the focus.

In terms of lighting, if you focus the camera in bright lighting, the iris is smaller to prevent light from washing out the image. However, as the day progresses and natural light diminishes, the iris opens wider to let in more light and capture more detail, resulting in a reduced depth of field and blurry images. This issue can be resolved by placing a neutral density filter on the lens to simulate low-light conditions, or by switching to manual iris mode to maintain consistent footage throughout the day.

Additionally, ensure that your camera lens is clean. Dirt or foreign objects on the lens can interfere with autofocus, leading to poor focus. Use a soft, dry, lint-free cloth to gently clean the lens. Also, check that your phone case or accessories do not obstruct the lens, as this can also impact the camera's ability to focus.

Regarding the background, when the camera focuses on a single subject, the background area may naturally appear out of focus. If you are experiencing issues with the background being blurry, try disabling the "Tracking auto-focus" feature. This feature locks the focus on a selected subject for a few seconds, which may give the impression that the camera is not focusing on the entire scene. By turning off this setting, you can ensure that the camera focuses on the entire frame, including the background.

Camera lens cleanliness

Keeping your camera lens clean is essential to ensure the best image quality. Here are some detailed tips for maintaining optimal lens cleanliness:

Prevention:

• Always use a lens cap when the lens is not attached to the camera.
• Avoid changing lenses in dusty environments.
• Store your lenses in a dry, sealed space, such as a clean camera bag or lens pouch, to minimise dust accumulation.
• Regularly clean your camera bag to ensure the inside remains free of dirt and debris.
• Consider using a protective UV filter on the front of your lens to safeguard the lens from scratches and damage.

Cleaning Tools:

• Blower: Use a dust blower to remove large specks of dust and debris without risking scratches.
• Lens Brush: If there is remaining dust or residue, use a soft-bristled lens brush. Camel hair brushes are recommended for their thin, gentle bristles.
• Microfiber Cloth: For a final polish, use a soft, fine-weave microfiber cloth to wipe away any remaining streaks.
• Lens Cleaning Liquid: For stubborn smudges, watermarks, or fingerprints, use a small amount of lens cleaning liquid on a cloth or tissue, being careful not to leave streaks.

Cleaning Process:

• Blow Away Dust: Use a blower to remove loose dust and debris from the lens, preferably at a 45-degree angle with the lens facing upward.
• Brush Away Particles: If there are stubborn dust particles or residue, use a soft-bristled brush to gently sweep them away, being careful not to push down too hard.
• Apply Cleaning Solution: For a deeper clean, use a few drops of lens cleaning liquid on a lens cleaning tissue or microfiber cloth. Gently wipe the lens using a side-to-side or circular motion.
• Dry and Inspect: After cleaning, ensure the lens is completely dry and inspect it for any remaining smudges, oils, fingerprints, or grime. Repeat the cleaning process if necessary.
• Clean the Rear Element: Don't forget to clean the rear element of the lens using the same steps. This may require a Q-tip or the corner of a lens tissue for the smaller surface.
• Clean the Barrel: If the lens barrel is dirty, use the blower and brush to clean out any dust or dirt accumulated in the nooks and crannies. Be cautious when using liquids on the barrel, especially if the lens is not weather-sealed.

Remember, it is essential to clean your camera lens gently and only when necessary. Overcleaning can lead to scratches and damage to the lens coatings. Additionally, always use products specifically designed for lens cleaning, as other chemicals can be too harsh and cause damage.

Tracking autofocus

To enable tracking autofocus, you'll need to access your camera's autofocus settings. On Nikon DSLRs, for example, you can hold the AF button on the lower left side of the camera body and turn the main command dial until "AF-C" appears in the viewfinder or on the control panel. For mirrorless cameras, the AF modes are usually found in the menu system.

Once tracking autofocus is enabled, you can compose your shot. By half-depressing the shutter button (or using back-button focusing), your camera will start tracking the subject and continuously adjust the focus as it moves. This feature is particularly useful for capturing sharp images of fast-moving or unpredictable subjects, such as birds in flight or athletes in a football game.

It's worth noting that different camera brands and models may have variations in their tracking autofocus implementations. For instance, Nikon refers to their tracking autofocus as "Dynamic Area AF-C", while Canon uses the term "AI Servo AF." Additionally, some cameras offer advanced tracking features, such as Sony's "Real-time Tracking" and Nikon's "3D Focus Tracking."

While tracking autofocus is a powerful tool, it may not always produce perfect results. Factors such as lighting conditions, background complexity, and the speed and direction of the subject's movement can influence the effectiveness of autofocus tracking. In some cases, you may need to experiment with different autofocus settings or even disable autofocus and use manual focus to achieve the desired results.

Camera iris settings

The iris of a camera is an adjustable opening (aperture) that controls the amount of light that enters through the lens, also known as the "exposure". The wider the iris is open, the more light enters the camera, and the brighter the picture becomes. Conversely, closing the iris reduces the amount of incoming light, resulting in a darker image.

Professional cameras typically feature an iris ring on the lens housing, allowing users to physically adjust the aperture by turning the ring clockwise to close and anticlockwise to open it. On the other hand, consumer-level cameras often provide a dial or a set of buttons to adjust the iris settings. Additionally, you may need to select the "manual iris" option from the camera's menu; refer to your camera's manual for specific instructions.

Before using the manual iris mode, it is essential to understand the correct exposure for your camera. A good practice is to initially set your camera to auto-iris and frame a shot with even lighting. Observe the brightness of the image, and then switch to manual iris mode. Most cameras will maintain the exposure level set by the auto-iris, which you can then fine-tune as needed.

The fundamental rule of thumb for iris control is to prioritise the exposure of the subject. Ensure that your subject is appropriately exposed, even if it results in other parts of the image being too bright or too dark.

It is worth noting that the camera's autofocus feature can also impact its ability to maintain focus. If you are experiencing issues with the camera continuously going in and out of focus, you can try disabling the autofocus function.

Frequently asked questions