If you want to become a better photographer; learning the ins and outs of the camera is mandatory. Learning autofocus mode can be overwhelming when you are a beginner. Familiarize yourself with an array of buttons, dials, and menus – to understand how all those features work will allow you to take better and better photos.
In this quick guide, we provide an overview of what autofocus is and how it works, also how autofocus focuses on a subject.
What is Autofocus and how it works?
A camera’s autofocus system intelligently adjusts the camera lens to focus on the subject. In simple words, autofocus is a camera feature that ensures that your chosen subject is sharp within the photo.
Autofocus improves the quality of the picture. If you want to shoot like professional photographers, then knowing how the autofocus system works is essential to get sharp images. Once you know how autofocus works, you can easily capture perfect pictures that will make you, and your clientele happy. A precise focus translates to sharpening pictures and this is what everybody is seeing in photos today. In this technology world, most modern digital cameras are equipped with advanced autofocus systems such as canon.
The good thing about digital cameras is that they come with all types of essential autofocus. If back in the day, photographers manually focus to take a picture of a point. Now the autofocus system has made significant progress by lessening the number of failed photos. In today’s time, you just need to turn on autofocus mode and let the camera do all the work.
Moreover, this is how autofocus works; as the light enters the camera, it is sent through both the viewfinder and the mirror on the way to the AF module. This light is reflected in a prism and then towards the viewfinder behind the camera. The light is separated as it passes through that translucent part of the main mirror, where the sphere acts as a beam splitter. Two different pictures are focused downstream of the autofocus sensor below, where the two pictures are compared and their positions assessed. A system inside the camera appraises the signal from the autofocus sensor and directs the lens to adjust the focused elements inside the lens until both images are alike. Once the two images match, it tells the camera that the scene is in focus.
How does Autofocus focus on a subject?
Perhaps one of the most significant steps to capturing incredible photographs lies in understanding how your camera focus system works. There are two types of autofocus that the camera can use while focusing on the subject: phase detection and contrast detection.
Phase detection is generally considered the preferred method for all focusing scenarios, but chiefly for continuous autofocus and subject tracking. This is not only because of its capability to figure when focusing on a subject but also when an out-of-focus subject is back-focused or front-focused, letting the camera know in which way to move the lens to bring in its focus.
On the other side, contrast detection focuses the subject, when maximum contrast occurs in an image precisely. For contrast-detection to function properly, they need high contrast fields to focus on a subject. For example, autofocus cannot work on a plain white wall, the reason for this is that there is no contrast or transition in the wall that the camera can use to evaluate focus accuracy. Hence, the autofocus system needs high contrast for focusing on a subject. Each sensor of the camera measures relative focus by assessing the change of contrast at its corresponding point in the image – where extreme contrast is expected to correspond to an extreme sharpness.
Further, some other aspects can affect autofocus focus on the subject, such as the focus detection range of your camera, the speed of the focus motors, and the lens maximum aperture. The most important thing is focusing on the subject is that the photographer must keep the camera steady and ensure that the focus is full coverage. You also need to make sure that your subject is at the proper autofocus point, usually the center of the viewfinder.
The difference between one-shot, AI Focus, and AI servo
Let’s take a look at the different focus modes. Most professional cameras such as Canon, have two or three mains autofocus “drive” modes. They are One shot, AI Focus, and AI servo. AI Focus stands for Artificial Intelligence Focus. It is one of the three diverse automatic focusing modes available on Canon EOS DSLR cameras. It combines the features and deeds of the other two AF modes – One-Shot AF, and AI Servo.
the AI focus track constantly focuses until the subject stops, then locks the focus, and then the subject starts moving. So as long as the subject is still or might move slightly, using AI focus will be advantageous. This is because it will automatically focus on the new position as the subject shifts a little. It is the default autofocus mode on cameras. This mode is more useful when you change a focus or subject move.
AI servo focuses continuously and never locks. Autofocus always performs finest with action photos when using AI servo. It is also the name of Canon’s continuous-servo autofocus system, which continually tracks a subject. A photographer would use the AI Servo when they want to capture a picture of something moving, such as a football player, or a race car, for instance. This autofocus mode is beneficial for tracking moving subjects. This mode uses lots of battery power because it is continually focusing and refocusing. It works for both fast and slow-moving subjects
One Shot “is the term of Canon’s version of single-servo focus mode. One-shot focus works when neither you nor the subject is moving. AI servo focuses when you and the subject are moving forward. The one-shot is useful to capture the precise picture; when photographing a subject that doesn’t move, for example, a posing portrait. In single focus mode, when you press the shutter, the camera will focus on the subject once, lock that focus, and until you click the photograph. In this mode, when you release the shutter halfway, the camera focuses on the subject only once.
Hence, each autofocus mode is useful in different scenarios and has its cons and pros. The best thing is that you use it as needed that works for you the way you want it to work.
How to turn on AI servo and AI focus (canon)
In this article, you will learn how to turn on most Ai servo and Ai focus. Since the functionality of autofocus hinges on which camera type and model you are using, I visibly cannot go to all accessible AF modes, So I will only go through some camera systems. Since I am a canon user, I would put a bit more weight on canon cameras. Often cameras support an autofocus mode that continuously adjusts the focus distance for moving subjects.
AI servo is the best autofocus mode for fast-moving subjects. AI servo constantly focuses on the subject, to turn on the AI servo hold down the back button and click the shutter; when you have an image. It continuously focuses as long as you hold the back button. This lets you capture the picture without burst or sport mode because the camera is focusing on the act as it happens. You can click the perfect image as the camera waits without focusing again. As soon as you start releasing the shutter, the camera comes into action and starts focusing. In this mode, the camera detects the subject’s movements and focuses to take the sharp image.
Apart from this, Your camera may struggle for autofocus when there is not enough light, evenly colored scene. There will be no clear edge to finding the AF system. In this condition, the lens will focus back and forth, hunting for somewhat to lock onto. In AI-focus you press the shutter, the autofocus will constantly change focus to retain the subject sharpness. Moreover, the important aspect of AI focus, it will continue to monitor the distance on the subject, and if it will fluctuate, it automatically refocuses again. For reliable results though, you can choose AF mode and AF Area mode. The choice of AF mode determines how the lens will be focused; AF area mode determines where the camera will be focused on. By half-pressing the shutter button you first draw attention from your subject and lock it. It entirely depends on what you are shooting.
This guide will help you to understand autofocus mode. Nothing spoils a picture more than a blurred, uncertain image. However, in photography practice and experimentation are the real key to understanding how these things work.