08 What is FOCUS in Photography: Key Concepts Explained
Table of Contents Show
Introduction - What is focus in Photography
In the nuanced world of photography, the question of what is focus photography transcends the mere act of making subjects look sharp; it is central to the art and science of capturing images that evoke emotion, tell stories, and preserve moments. Mastery of focus—a blend of sharpness, depth of field, and the interplay of focus point photography—empowers photographers to direct viewers' attention effectively within a frame. The ability to manipulate focus photos through autofocus systems, controlling the focal plane, or employing techniques like focus stacking and hyperfocal distance is vital for achieving visual clarity and depth. This critical element determines not just the subjects' clarity but also the photograph's overall impact, making understanding photo focus essential for anyone looking to elevate their photographic work.
This article will explore the foundational aspects of focusing in photography, including the significance of focus points, the mechanics of camera focus, and how depth of field contributes to the perception of sharpness. It will delve into autofocus modes, from phase detection autofocus to AF-S, and the practical utilities of focus peaking and focus stacking. Additionally, readers will learn about techniques for achieving perfect focus pictures, overcoming common focusing challenges like "why won't my camera focus", and the role of the focus ring, among other focus techniques. By demystifying these concepts, the article aims to arm aspiring object photographers with the knowledge to harness focusing to its full potential, transforming their approach to photography through precision, creativity, and control.
The Science Behind Camera Focusing: What You Need to Know
The Basics of Camera Focusing
At its core, camera focusing is the process of adjusting the lens to achieve optimal sharpness and clarity for the desired subject or area within the scene. This is accomplished by converging the light rays from the subject onto the camera's image sensor or film plane, resulting in a precisely focused image.
What is Camera Focusing?
Camera focusing is the act of finding the optimal sharpness of an object within the frame. A completely sharp image is said to be in focus, while a blurry or indistinct image is considered out of focus. The focusing mechanism works by adjusting the distance between the lens and the image sensor or film, allowing light to converge precisely at the desired plane.
Types of Camera-Focusing Systems
There are several types of focusing systems employed in cameras:
Split-Image Rangefinder: This system displays two images of the subject, which align and merge when the subject is in focus.
Matte Field: A matte surface within the viewfinder aids in quick shooting and low-light situations.
Microprism Ring: This system consists of numerous tiny prisms and is useful for focusing on subjects lacking distinct vertical elements.
Phase Detection Autofocus: Found in modern DSLR cameras, this system uses a dedicated autofocus sensor to detect and achieve focus by analysing the phase differences between light rays.
Contrast Detection Autofocus: Common in mirrorless cameras and live view modes, this system analyses the image’s contrast on the primary sensor to determine and adjust focus.
How Autofocus Works in Modern Cameras
Modern cameras employ two primary autofocus (AF) systems: phase detection and contrast detection. These systems work in tandem to provide accurate and efficient focusing capabilities.
Phase Detection
Phase detection AF is a hardware-based system that uses an array of microlenses to split incoming light into pairs of images. By measuring the distance between these image pairs, the camera can determine whether the subject is front or back-focused. This information is then used to instruct the lens on how to adjust its focus accurately.
The phase detection system works as follows:
Light enters the lens and is partially reflected by the primary mirror onto a dedicated AF sensor.
Microlenses on the AF sensor divide the light into pairs of images for each active AF point.
The separation between these image pairs is analysed to calculate the required degree and direction of focus adjustment.
The camera instructs the lens to move its focus ring accordingly until the subject is perfectly sharp.
Phase detection AF is swift and precise, making it ideal for tracking moving subjects in sports or wildlife photography.
Contrast Detection
Contrast detection AF relies on software algorithms to analyse the contrast levels within the image captured by the camera's main sensor. The system scans the scene, rapidly adjusting the lens focus until the highest contrast (sharpest detail) is achieved for the desired subject.
While contrast detection AF is generally slower than phase detection, it offers superior accuracy for stationary subjects. It works by:
Evaluating the contrast levels across the image sensor.
Adjust the lens focus incrementally while monitoring contrast changes.
Locking focus when the maximum contrast is detected, indicating optimal sharpness.
Hybrid Systems
Many modern cameras combine phase detection and contrast detection AF into a hybrid system, leveraging the strengths of both technologies. This approach allows for fast and accurate focusing in various shooting scenarios.
Hybrid AF systems can switch between phase detection for quick subject acquisition and contrast detection for precise fine-tuning. Some advanced implementations combine data from both systems simultaneously, resulting in exceptional autofocus performance.
By understanding how these autofocus systems operate, photographers can better utilise their camera's capabilities and capture sharper, more compelling images.
Basic Concepts of Focus
Understanding the fundamental concepts of focus in photography, such as the plane of focus and depth of field, is essential for photographers aiming to enhance their visual storytelling and create compelling compositions. These concepts are intricately linked to how a photographer controls what appears sharp in an image and what is softened into an out-of-focus blur, effectively directing the viewer's attention.
Plane of Focus
The plane of focus is a critical concept in photography, referring to the specific area within a scene that is in sharp focus. It can be visualised as an imaginary line or plane that extends across the frame, parallel to the camera's sensor. When a camera lens is focused on a subject, this plane is perfectly sharp, and anything before or after this plane begins to lose sharpness, depending on the aperture setting.
For instance, imagine positioning subjects along a straight line in an open field; if they align precisely with this focal plane, they will all appear sharply focused, even at a wide aperture like f1.4. However, if a subject moves slightly forward or backwards away from this line, it will fall out of focus. The width of this plane of focus can be adjusted by changing the aperture: a lower f-stop number (like f1.4) results in a narrower plane, while a higher f-stop number broadens the focus area.
Depth of Field
Depth of field (DoF) describes the extent of the area in the photograph that appears acceptably sharp. It extends in front of and behind the plane of focus and is influenced by several factors, including aperture size, the distance between the camera and the subject, and the lens’s focal length.
Aperture: Smaller apertures (higher f-stop numbers) increase the depth of field, rendering a larger area of the scene in focus. Conversely, larger apertures (smaller f-stop numbers) create a shallow depth of field, focusing sharply on the plane of focus while blurring the foreground photography and background.
Distance to Subject: The closer the subject is to the camera, the shallower the depth of field. Moving the subject away from the camera increases the depth of field.
Focal Length: Longer focal lengths reduce the depth of field, making it easier to isolate the subject from distracting backgrounds with a pleasing blur. Shorter focal lengths increase the depth of field, keeping more of the scene in focus.
By mastering these concepts, photographers can manipulate the plane of focus and depth of field to create images that isolate the subject dramatically or include detailed context by keeping the entire scene in sharp focus. Experimentation with these settings allows photographers to achieve their desired artistic effects, whether capturing the intricate details of a portrait or the expansive beauty of a landscape.
Autofocus Modes Explained
Understanding the different autofocus modes is crucial for photographers to effectively capture their subjects under varying conditions. Two primary modes dominate most modern cameras: Single-Servo AF (AF-S) and Continuous-Servo AF (AF-C), each serving distinct purposes and scenarios.
Single-Servo AF
Single-Servo AF, known as AF-S, is ideal for stationary subjects. When the shutter button is half-pressed, the camera focuses once and locks the focus. This mode prevents the focus from changing even if the camera slightly moves, making it perfect for landscapes, still-life, or posed portraits. It's widely used because it allows photographers to recompose their shot after focusing, ensuring the subject remains sharply in focus despite any repositioning of the frame. For instance, in Canon systems, this is referred to as One-Shot AF, while Sony labels it Single-Shot AF.
Continuous-Servo AF
Continuous-Servo AF, or AF-C, is designed for moving subjects. It continuously adjusts the focus as long as the shutter button is half-pressed, tracking the subject's movement across the frame. This mode is essential for sports, wildlife, or any dynamic scene where the subject is in constant motion. The camera predicts the subject's next position to maintain sharp focus throughout the shooting process. Manufacturers might name this mode differently; Canon calls it AI Servo AF, Nikon as AF-C, and Sony as Continuous AF.
Both modes have their specific applications and choosing the right one depends on the nature of the subject and the photographic scenario. For static subjects or when precise focus placement is crucial, AF-S is preferred. Conversely, for capturing action or fast-moving subjects, AF-C offers the responsiveness needed to keep the subject in focus despite rapid movement. Understanding these modes enhances the photographer's ability to handle various shooting environments, ensuring high-quality captures in all conditions.
Manual Focus
Manual focusing on the camera is a fundamental skill that every photographer should master. By taking control of the focus manually, photographers can ensure that the subject is sharp and crisp in the image. To manually focus, adjust the focusing ring on the lens until the subject appears sharp in the viewfinder or on the camera's LCD screen. This technique is especially useful in low-light situations or when the camera's autofocus struggles to lock onto the subject. Practice and patience are key to mastering manual focusing, but the results are well worth the effort, allowing photographers to have full control over their compositions.
Autofocus Area Modes Explained
Auto focus area mode in photography allows the photographer to select the specific area in the frame where they want the camera to focus. This feature is particularly useful when capturing subjects that are off-center or when there are multiple subjects at different distances in the frame.
By choosing the autofocus area mode, photographers can ensure that the camera focuses exactly where they want it to, resulting in sharper images with the intended subject in clear focus. Different cameras offer various autofocus area modes, such as single-point AF, zone AF, and wide AF, giving photographers the flexibility to adapt to different shooting scenarios and achieve desired results.
Single Point Area Mode
The user selects the specific focus point to use by aligning it to their subject
Dynamic Area Mode
The user selects the specific focus point but if the selected subject moves the camera adjusts the focal point used to the moving subject
Auto Area Mode
The camera selects the specific focus point based on what it thinks is the subject!
Eye or AI Area Mode
The camera automatically recognises the subject, human, eye, animal and so on and quickly focuses appropriately. This new recognition technology is improving all the time.
Techniques for Achieving Perfect Focus
Focus and Recompose
The technique of focus and recompose is particularly useful when photographers face limitations with autofocus points, especially in low-light conditions where the lens may struggle to find focus. By setting the camera to Single Servo (AF-S) mode, one can ensure the focus is acquired once and maintained, even when recomposing the shot. This method involves focusing on the subject with a half-press of the shutter button, then while keeping the button half-pressed, the camera is moved to reframe the shot. It's crucial, however, to be cautious with this technique when using wide apertures or shooting at close distances, as the focus plane shifts and could lead to a defocused subject.
Back-Button Focus
Back-button focusing separates the tasks of focusing and shutter release, allowing photographers greater control, particularly in dynamic environments. By assigning the autofocus activation to a button on the back of the camera, such as the AF-On button, the photographer can focus with the thumb and shoot with the index finger independently. This setup is ideal for action photography where subjects move unpredictably, such as in sports or wildlife photography. For instance, during a football game, a photographer can keep the focus on an athlete by holding the back button and capture the perfect moment without worrying about refocusing due to any intervening players or objects.
Focus Stacking
Focus stacking is a sophisticated technique used to extend depth of field in photography. This method is particularly beneficial when dealing with macro photography or any scenes requiring front-to-back sharpness. It involves taking multiple photos at different focus distances and blending them to create a single image with greater depth of field than any single shot could achieve. Using a tripod is essential to maintain consistent framing across shots, and manual focus is recommended to adjust the focus precisely for each shot. After capturing the necessary images, software like Photoshop can be used to align and blend these layers effectively, ensuring a sharp composite image across the entire frame.
By mastering these techniques, photographers can tackle various focusing challenges and enhance the sharpness and clarity of their images, regardless of the shooting conditions or subject matter.
Common Focusing Challenges and Solutions
Low light conditions can significantly impact the effectiveness of autofocus systems, often leading to blurry or out-of-focus images. To combat this, photographers can employ several strategies to enhance focusing accuracy:
Use a Lens with a Wider Maximum Aperture: A lower f-number allows more light to enter the camera, aiding the autofocus system in low light situations.
Increase ISO Sensitivity: Boosting the ISO makes the camera more responsive to light, albeit at the risk of increased noise or grain in the images.
Enable Built-In Focus Assist Light: Many cameras come equipped with a focus assist light that helps the autofocus system by illuminating the subject.
Switch to Manual Focus: In scenarios where autofocus continually struggles, manually focusing the lens ensures control over the sharpness and clarity of the subject.
Place a lit subject in the scene where you want the focal plane/DoF to start - lock focus on it, then switch to manual focus without changing anything -else. Remove the lit object, phone, torch or whatever you used to lock focus on and take your picture.
Fast Moving Subjects
Focusing on fast-moving subjects presents another set of challenges as the autofocus system may fail to maintain a lock on the subject, especially when it moves rapidly across the frame. The following techniques can improve focus accuracy for dynamic subjects:
Use High-Speed Continuous Autofocus Mode: This mode is better equipped to track and maintain focus on moving subjects.
Adjust Autofocus Sensitivity and Speed: Increasing these settings can enhance the camera's responsiveness, making it quicker to adjust focus as the subject moves.
Pan with the Subject: Matching the camera's movement with the subject's speed and direction helps maintain focus by keeping the subject in a consistent position within the frame.
Anticipate the Subject's Movement: Focusing on the area where the subject is expected to move allows the photographer to capture the subject sharply as it enters the pre-focused zone.
By understanding and applying these solutions, photographers can address common focusing challenges effectively, ensuring sharp and clear images even in demanding shooting conditions.
Conclusion - What is focus in Photography
Throughout this article, we have delved into the pivotal role of focus in photography, uncovering its capability to transform images by guiding the viewer's attention, enhancing story-telling, and achieving desired emotional impacts. From the foundational knowledge of focus points and depth of field, to the intricacies of autofocus modes and manual focusing techniques, we have explored the various aspects that photographers must master to capture vivid, impactful images. The discussed strategies and solutions to common focusing challenges serve as a testament to the blend of art and science that photography embodies, empowering both novice and experienced photographers to harness focus as a powerful tool in their creative arsenal.
As we conclude, it's clear that understanding and manipulating focus is essential for creating visually stunning and meaningful photographs. The journey to mastering focus is one of both technical precision and creative exploration, where photographers are encouraged to experiment with various techniques to overcome challenges and realise their artistic visions. Embracing the complexity of focusing on photography not only elevates the quality of one's work but also nurtures a deeper appreciation for the art form itself. As you continue to explore the vast world of photography, let the knowledge and techniques shared here inspire you to push the boundaries of focus, crafting images that resonate with clarity, depth, and emotion. I teach the practical use of camera settings on all my outdoor workshops or with my private lessons and my photography evening course lessons.
FAQs - What is focus in Photography
1. What does focus mean in photography?
Focus in photography refers to the area of the image that appears sharpest. It is crucial for drawing attention to a specific object, person, or scene, and is a fundamental aspect of photography alongside ISO, aperture, and shutter speed. Photographers can choose between automatic or manual focusing techniques.
2. What is the general rule for setting focus in photography?
When using a wide-angle lens, the focus point should generally be positioned about one-third of the way up from the bottom of the frame. If using a telephoto lens, the focus should typically be on the nearest or most significant element in the frame.
3. What should be the primary focus in a photograph?
In portrait photography, the eyes of the subject are usually the most compelling focal point, as they tend to draw the viewer's attention first. This holds true regardless of the aperture setting, unless the artistic intent of the photograph dictates otherwise.
4. What are focus modes in photography?
Focus modes in cameras determine whether the camera uses autofocus or manual focus. This setting can often be adjusted using a physical switch marked "AF/MF" or through a specific dial and/or button on the camera.