Focusing Analog Surveillance Cameras: A Step-By-Step Guide

Focusing an analog surveillance camera is a skill that can be developed with practice. The process involves adjusting the in-focus region to be closer or further from the camera, usually by rotating the focusing ring on the lens while autofocus is disabled. Manual focus is particularly useful in low-light settings, astrophotography, and scenarios where autofocus struggles, such as with transparent or low-contrast subjects. Additionally, manual focus can offer more precision when working with still subjects in a studio setting. It is important to note that autofocus, on the other hand, is generally faster and more precise than manual focus, especially in modern SLR cameras with through-the-lens optical sensors.

Understand the difference between manual and autofocus

Autofocus (AF) and manual focus are two different methods of achieving the same goal: a clear, crisp image. Both types of focus aim to set the point of focus to obtain a sharp image of the desired subject. However, there are distinct differences between the two methods, and each has its own advantages and disadvantages.

Autofocus

Autofocus systems use a combination of sensors, control systems, and motors to automatically determine and set the point of focus. The number of sensors used varies, with some AF systems relying on a single sensor, while others use an array of sensors. AF systems rely on contrast to identify objects, and they can struggle in low-light conditions or when there are multiple objects in the scene.

The benefits of autofocus include:

• Speed: It is generally faster than manual focus, making it suitable for capturing moving subjects or action shots.
• Ease of use: The photographer does not need to manually adjust the focus, allowing them to focus on other aspects of the shot.
• Continuous focus: AF systems can continuously track moving objects and adjust the focus accordingly.

The drawbacks of autofocus include:

• Lack of precision: Autofocus may not be as precise as manual focus, especially for macro photography or when there are multiple objects in the scene.
• Shutter lag: AF systems can cause some shutter lag if not pre-focused properly.
• Focusing on the wrong subject: In certain situations, AF may focus on the wrong part of the subject or the wrong subject entirely.

Manual Focus

With manual focus, the photographer sets the point of focus by hand. This method gives the photographer greater control over the shot and allows for more precise focusing. Manual focus is particularly useful in low-light conditions, when shooting through windows, or when there are multiple objects in the scene, as it allows the photographer to choose the specific object to focus on.

The benefits of manual focus include:

• Precision: It allows for more precise control over the focus, especially for macro, portrait, and low-light photography.
• No autofocus errors: Manual focus eliminates the possibility of the camera focusing on the wrong part of the subject or the wrong subject entirely.

The drawbacks of manual focus include:

• Speed: It is generally slower than autofocus, making it less suitable for capturing moving subjects or action shots.
• Difficulty with moving subjects: Manual focus can be challenging for action shots or scenes with moving subjects, as the focus point needs to be constantly adjusted.

Both autofocus and manual focus have their strengths and weaknesses. Autofocus is generally faster and more convenient, making it suitable for capturing moving subjects or action shots. On the other hand, manual focus offers greater control and precision, making it ideal for macro, portrait, and low-light photography. The best focus method depends on the specific situation and the photographer's preferences.

Learn how to enable manual focus on your camera

Learning how to enable manual focus on your camera can be a valuable skill to have, especially when autofocus fails you. Here's a step-by-step guide on how to do it:

Step 1: Understand Manual Focus

First, let's understand what manual focus is. Almost all camera lenses have the ability to adjust focus. Focusing is the process of changing how the lens projects light by moving the lens elements or the entire lens itself. Manual focus is when you adjust the focus manually to make an object appear "in-focus" and sharp, with the surrounding areas becoming less sharp. This is usually done by rotating the focusing ring on your lens while autofocus is disabled.

Step 2: Locate the Focusing Mode Switch

On your camera or lens, locate the focusing mode switch, which is typically labelled with "AF/MF". This switch allows you to toggle between autofocus (AF) and manual focus (MF). By switching to "MF", you disable autofocus and enter manual focus mode.

Step 3: Find the Focus Ring

The focus ring is what you'll use to manually adjust the focus. It is often located near the middle of the lens barrel for prime lenses or near the end of the lens barrel for zoom lenses. By twisting the focus ring, you can change the point of focus, bringing different areas of the scene into focus.

Step 4: Adjust the Focus

Look through your camera's viewfinder and twist the focus ring. You should see the focus shift as different parts of the image go in and out of focus. Continue adjusting the focus ring until your desired subject is in focus. This may take some practice to perfect, but it's a valuable skill to have.

Step 5: Check Your Results

After manually focusing and taking a photo, be sure to check the result on the camera's LCD screen. Zoom in on the image to ensure that you've achieved the desired sharpness and focus. This step is crucial to ensure that your manual focus efforts were successful.

Bonus Tip: When to Use Manual Focus

While autofocus is convenient and works well in most situations, there are times when manual focus is preferable or necessary. Here are a few scenarios where manual focus can be beneficial:

• Low Light Conditions: Autofocus may struggle in low-light environments, especially when there is insufficient contrast. In such cases, manual focus can be a more reliable option.
• Specific Focus Distance: If you want to focus on a specific point in the scene, such as a subject entering the frame at a particular location, manual focus allows you to set the focus distance in advance and ensure the camera doesn't focus elsewhere.
• Creative Control: Manual focus gives you complete control over the point of focus, allowing for creative techniques such as intentional camera movement, deliberate misfocusing, or shoot-through effects that may be challenging with autofocus.
• Macro Photography: Autofocus can struggle with macro subjects, especially when working at high magnifications. Manual focus gives you precise control over the focus, ensuring that the tiny details of your subject are sharp.
• Shallow Depth of Field: When working with wide apertures that have a narrow depth of field, manual focus can help ensure that the critical areas of your image are in focus.

Remember, while manual focus can be a powerful tool, it's not always the best option. Autofocus is generally more suitable for fast-paced or action-packed scenes, such as sports or wildlife photography, where quick focus acquisition is essential.

Know when to use manual focus

Manual focus is a great skill to have as a photographer. While autofocus is useful in many situations, there are times when you'll get better results by focusing manually. Here are some scenarios where you should consider using manual focus:

Low Light Conditions

Low-light situations, such as a candlelit reception or a dark street, can be challenging for autofocus systems. In these cases, it may be easier to switch to manual focus. This is especially true for older cameras, as newer cameras can often autofocus in very low light conditions. Astrophotography is a great example of when to use manual focus, as it involves very low light and precise focus.

Action in a Specific Location

If you're expecting action to occur in a specific location, such as a baseball player sliding into home plate or a bride entering a church, you can set your focus manually on that point in advance. That way, you can capture the moment without worrying about finding focus.

Autofocus Confusion

There are times when autofocus struggles, such as with low-contrast subjects (e.g., a dark subject on a black background) or transparent subjects. In these cases, the autofocus may hunt continuously without locking onto the subject. Setting the focus manually may be easier and faster than fighting with the autofocus system.

Shallow Depth of Field

Lenses with fast apertures like f/1.4 and telephoto focal lengths often have a very narrow depth of field, which can challenge autofocus systems. Manually focusing in these situations may give better results. This is a common technique used by macro photographers, who manually focus by rocking forward and backward to get the perfect shot.

Studio Photography

When working in a studio with still subjects, manual focus can be a great option. With your camera typically on a tripod, it's easier to adjust the focus manually, and you can be very precise with your focus placement.

While autofocus is convenient and useful in many situations, there are times when manual focus is the better choice. By knowing when to use manual focus, you can improve the sharpness and quality of your images and become a more versatile photographer.

Get sharp results with manual focus

Manual focus is a skill that requires practice and dexterity, especially when working with moving subjects. Here are some tips to help you get sharp results with manual focus:

• Practice: The more you practice manual focusing, the better you will become at it. It's a skill that requires muscle memory, so the more you do it, the more intuitive it will become.
• Understand the basics: Manual focus works based on distance. By rotating the focusing ring on your lens, you can adjust the in-focus region to be closer or further from the camera. Turning the ring clockwise will focus on objects that are closer, while turning it counterclockwise will focus on objects that are farther away.
• Use Live View: Using the LCD screen instead of the viewfinder can make it easier to see if your shot is sharp. Zoom in on your subject to make it easier to determine if they are in focus as you turn the focus ring.
• Pre-focus for action: If you know where the action is going to take place, you can pre-focus on that spot to capture sharp shots without missing the moment. This works well for subjects with predictable movement patterns.
• Use camera-assisted manual focus: Many cameras have features to help with manual focus. For example, Nikon cameras have a circle that appears in the viewfinder when your image is in focus, while Canon cameras have a focus confirmation light.
• Use a loupe: A loupe is a tool that magnifies the camera's rear screen and blocks glare, making it easier to gauge focus.
• Use the magnifying button: Many cameras have a simple magnifying button that allows you to zoom in on the live view screen, making it easier to see if your subject is in focus.
• Use autofocus indicators: Even when in manual focus mode, many autofocus systems will still be working. Indicators such as brackets and dots can help guide you in adjusting the focus.
• Use focus peaking: Many newer cameras support focus peaking, which outlines objects that are in focus in bright colors. This can be very helpful when using fast lenses with a narrow depth of field.
• Widen your depth of field: If you're having trouble nailing the focus, try widening your depth of field by using a smaller aperture value, stepping back, or using a wider-angle lens. This will give you more leeway when focusing.

Understand autofocus accuracy and speed

Autofocus (AF) systems rely on sensors to determine the correct focus. The number, position, and type of sensors in a camera's AF array influence its autofocus accuracy and speed. Here are the key factors to understand:

Number of AF Points

The number of AF points in the array impacts the area of the frame that can be covered. More AF points generally mean a wider area can be focused on, which is advantageous for tracking moving subjects. High-end cameras often have more AF points, with some models offering 45 or more, while entry-level cameras may have as few as one central AF point.

Position of AF Points

The position of AF points determines where the camera can focus. Cameras with more AF points provide greater flexibility in composing shots, as you can select specific points to focus on. The centre point in the array is typically the most accurate and is often a cross-type point, sensitive to both vertical and horizontal orientations.

Type of AF Points

There are different types of AF points, including vertical, horizontal, and cross-type sensors. Vertical and horizontal sensors are one-dimensional, detecting contrast in only one direction. Cross-type sensors are two-dimensional and can detect contrast in both vertical and horizontal lines, making them more accurate. Cameras with more cross-type sensors generally provide better autofocus accuracy and handle challenging situations better.

AF Modes

Different AF modes also impact accuracy and speed. The main modes are:

• Single-point AF: You select a single focus point, and the camera focuses only on that point.
• Dynamic AF: You choose an initial focus point, and once focus is achieved, the camera uses surrounding points to track subject movement.
• Auto-area AF: The camera automatically selects the focus point, usually focusing on the closest or largest object in the frame.
• Continuous AF: The camera continuously adjusts focus, predicting the subject's future position based on its velocity. This mode is ideal for moving subjects but consumes more battery power.

Lens Aperture

The maximum aperture of the lens also affects autofocus accuracy and speed. Larger apertures (e.g. f/2.0 to f/2.8) are generally faster and provide better autofocus performance. Smaller apertures, such as f/5.6, may result in slower autofocus operation due to reduced light passing through the lens.

Other Factors

Other factors that can influence autofocus accuracy and speed include the quality of light, focus detection range, speed of focus motors, and the overall reliability of the AF system. Additionally, some cameras offer autofocus assist features, such as an AF assist beam, which can improve autofocus performance in low-light conditions but may slow down the process.

Frequently asked questions