Modern cameras offer many options when it comes to choosing the focus modes on your camera. In this article we will discuss some of the options generally available in todays cameras.
With most cameras there will be a manual mode and several automatic modes of focussing.
Manual Mode Focussing
In manual mode the camers does not focus at all. The photographer will adjust the lens focussing until the image in the viewfinfer is in focus using the focussing ring on the lens barrel.
Automatic Mode Focussing
In the automatic mode, modern cameras will generally provide from up to 50 or more focussing points, which the photographer can select, for the camera to automatically focus on. Generally single or groups of focus points can be selected for the camera to focus on.
Some of the more sophisticated cameras will offer several modes for automatic shooting. The automatic metering mode will generally be activated by half pressing the camera shutter button.
The following modes may be available on the better quality cameras.
Single Servo Autofocus Mode
This mode will be activated and the camera focus will lock when the shutter button is half pressed and an indicator in the viewfinder may indicate that the image is in focus. Some cameras will only operate the shutter when the focus indicator in the viewfinder is on.
Some cameras will have predictive tracking so that if the subject is moving at the time the shutter is half pressed, the camera may track the subject until the subject is in focus and then the shutter is released to capture the image. There will be a delay between pressing the shutter button and the shutter operating while the camera focusses.
Continuous Servo Autofocus Mode
In this mode the camera will focus continuously while the shutter release button is half pressed and the focus will be adjusted as the subject moves. The image can be take even if the camera indicates that the image is not in focus. Focus does not lock when the subject stops moving.
Autofocus On Button
Some cameras provide an auto focus on button, which simulates the half pressing of the shutter button.
Autofocus Area Mode
This mode enables the photographer to select what happens if the subject moves while the camera is still focussing. The following is an example of some of the modes which may be available for selection.
- Single Area Auto Focus – Here the user can select a focus area manually for the camera to focus on. This is generally suitalbe for static subjects
- Dynamic Area Auto Focus – Here the user also selects a focus area but the camera will use information from other focus points to keep the subject in focus if it is moving eratically
- Group Dynamic Auto Focussing – The photographer can select a group of focus areas and the camera will select the focus point closest to the camera from that group of points
- Closest Subject Priority Focussing – In this mode the camera will automatically select the focus point which contains the subject closest to the camera
- Focus Lock – A focus lock button may be oprovided to change the composition of the image after the camera has already locked on to a subject.
In getting the camera to focus accurately there are some important issues you may need to consider to ensure more accurate focussing.
- A camera will focus better if there is a change in contrast at the focus point
- If the subject is very small the camera may have difficulty in focussing
- If there is a lack of variation in brightness then the camera may have difficulty in focussing
- If the focus point contains objects at different distances from the camera there may be some difficulty in focussing.
Auto Focus Assist Illumination
Some cameras will have an auto focus illumination assist light and in difficult lighting situations this will assist the camera to focus more accurately. Also some speedlights will provide an auto assist light to help the camera focus more accurately.