Camera “Autofocus” Basics

It’s been awhile since my last post as I have been working on how to simplify a complex subject to explain controlling the camera’s autofocus system by covering the basics of what you need to know to start getting sharp images.

The camera’s focusing system plays the primary role in helping you achieve a sharp image. Depending on the type of camera there are a number of aspects that we need to discuss, to learn how to set the camera focusing system to best match your shooting scenario.

Acquiring focus, with the default settings, will start when you push the shutter button 1/2 way down while pointing at a subject of interest. At this moment, the camera will determine the exposure and focus the lens simultaneously within fractions of a second. However, we need to understand what focus settings are best for each shooting scenario to know how to set them accordingly.

We will discuss the basic settings of the focus system by breaking it down into three parts; (1) Focus mode switch (selecting autofocus or manual), (2) Autofocus mode (choosing a single or continuous autofocus mode), and (3) Focusing area (setting a focus point or focus area), is the most complex part of the focusing system.

©Trevor Awalt_Lens Autofocus Setting Canon17-40mm(1) Focus mode switch: DSLR’s, with Canon the Focus mode switch is typically located on the barrel of the lens. Set the switch to the “AF” position to enable autofocus. If you set the switch to the “MF” position autofocus is disabled, then you are required to manually adjust the focus by turning the focusing ring on the lens. For most situations, typically set the mode switch to “AFposition.

For Nikon the designations are “M/A”, autofocus with manual override, and “M” for manual.

©TrevorAwalt_Canon-Control Dial_Focus Modes When using a bridge camera such as a Canon SX30, or a compact camera such as the Canon SX100, access the Focus mode by first pressing the left “◄” of the “control dial“. Then press the left “◄” or right “►” of the “control dial” to select one of the three (3) focus modes; Macro (autofocus for close subjects), Normal (autofocus for non-close subjects), and Manual (manual focus mode).  To accept the setting press the “func/set” button located in the center of the “control dial“.

When using an iPhone with the native camera app you do not have the ability to manually focus, if you want manual focusing capability choose a third party camera app, for example; Camera+, ProCamera or VSCO. Refer to their respective manuals to learn how to switch between the auto or manual focus setting.

(2) Autofocus modes: DSLR’s, with Canon there are typically three autofocus modes to choose from; One Shot, AI-Focus, and AI-Servo. (A) The “One Shot” setting is best used for subjects that are not moving, (B)AI-Focus” will automatically switch between “One Shot” if the subject is stationary and “AI-Servo if the camera detects the subject is moving, and (C) the “AI-Servo” setting is best used for subjects that are moving.

For Nikon the three autofocus modes to choose from are; (A)AF-S” (Single-servo autofocus for stationary subjects), (B) “AF-A” (Auto-servo autofocus the camera automatically switches between AF-S if the subject is stationary or AF-C if the camera detects the subject is moving), and (C)AF-C” (continuous-servo autofocus for moving subjects).

When using a bridge camera such as a Canon SX30, there are two autofocus modes to choose from; (A) Servo AF Off or (B) Servo AF On, accessed by pressing the menu button and then the “▲” or “▼” on the control dial, then use the “◄” or “►” to change the setting. Servo AF Off is used for stationary subjects while Servo AF On is used for moving subjects.

When using a compact camera such as the Canon SX100, there are two autofocus modes to choose from; (A) Single or (B) Continuous, accessed by pressing the menu button and then the “▲” or “▼” on the control dial, then use the “◄” or “►” to change the setting. Single is used for stationary subjects while Continuous is used for moving subjects.

With an iPhone you tap the screen where you want to focus and the camera is in continuous focus mode, if you tap and hold, the AE/FE lock will appear and at that point the camera holds that focus setting.

(3) Focusing Area: DSLR’s, depending on the camera capabilities will vary. With a Canon T6i for example there are three Focus areas to choose from; Single-point AF, Zone AF, and 19-point auto select AF. (A) Single-point AF allows the user to manually select any one of the 19 focus points. (B) Zone AF allows the user to manually select groups of focus points. (C) 19-point auto select AF allows the camera to select the focus point that is closest to the subject. Starting out the recommended setting would be (B) Zone AF as the user has the ability to manually move the groups to an area to satisfy the desired composition.

For a Nikon D5100 for example there are four Focus areas to choose from; Single-point AF, Dynamic-area AF, 3D-tracking, and Auto-area AF. (A) Single-point AF allows the user to manually select any one of the 11 focus points. (B) Dynamic-area AF allows the user to manually select the focus point with the camera using adjacent focus points to help keep the subject in focus. (C) 3D-tracking allows the user to manually select the initial focus point which then allows the camera to track the subject focused on by using all the focus points. (D) Auto-area AF allows the camera select the focus point that is closest to the subject. Starting out the recommended setting would be (C) 3D-tracking.

When using a bridge camera such as a Canon SX30, there are three Focus areas to choose from via the AF Frame menu option; FlexiZone, Center, and Face Detect. (A) FlexiZone is for focusing on a specific point where the user can change the size and position of the frame. (B) Center locks the frame to the center. (C) With Face Detect the camera automatically tries to detect peoples faces, locks on and attempts to follow the subject to keep the subject in focus. Starting out the recommended setting would be (A) FlexiZone.

When using a compact camera such as the Canon SX100, there are two focus areas available via the AF Frame menu option; Center and Face Detect. (A) Center locks the frame to the center. (B) With Face Detect the camera automatically tries to detect peoples faces, locks on and attempts to follow the subject to keep the subject in focus. Starting out the recommended setting would be (A) Center.

With an iPhone the only focus area is the box that appears when you tap the screen. If you do not tap an area on the screen the camera will decide on what it thinks is the focus point. Starting out the recommended operation is to tap the screen where you want the camera to focus.

Take time to go over this lesson concentrating on the sections that best apply to your camera. The focus system is something that will take time to master and with more practice you will eventually be able to understand and control the appropriate settings to achieve sharp images.

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