Dual Pixel CMOS AF is an autofocus technology developed by Canon that aims to deliver the speed and responsiveness of phase detection autofocus using only the camera sensor and not a separate phase detection sensor. This has many advantages for mirrorless cameras and DSLRs being used in live view mode. Effectively, the photosites on Canon’s […]
Autofocus explained
Almost all modern cameras have an autofocus system, where the camera automatically focuses the lens on a subject in the picture. They do this with multiple focus points arranged around the frame. You can choose the focus point you want the camera to use, or you can let the camera choose the focus point automatically – it will usually choose the subject nearest the camera. Here are some more articles about autofocus, the different technologies used and how to get the best results.
STM (Canon)
STM stands for stepper motor lenses, a new type of autofocus motor used by Canon in some of its lenses. Stepper motors offer fast, precise and quiet focus adjustments, so these lenses are well suited both to regular stills photography and to video, where autofocus noise can be picked up very easily by the camera’s […]
Stepping motor
As the name suggests, stepping motors move in small, incremental steps. They are simple, reliable and offer a good deal of control and precision. They’re now being used by Canon (STM lenses) and Nikon (AF-P lenses) in a number of consumer-orientated lenses, where they offer fast, quiet and smooth autofocus.
AF-P (Nikon)
This is a new autofocus technology being introduced by Nikon in its consumer-level lenses. It used different autofocus actuators to its existing AF-S (Supersonic Wave) lenses. The AF-P system uses stepper motors for a fast, quiet and smooth autofocus action that’s especially well suited to video, where you don’t want fast, sharp focus movements or […]
Touch AF
Autofocus mode where you tap on a touch-sensitive screen to choose the focus point for the picture. Some cameras also offer a touch shutter option where tapping the screen not only sets the focus point but fires the shutter too.
Subject tracking autofocus
A focus mode where the camera continually refocuses on a moving subject. The more advanced the AF system, the better it will be at keeping the subject in focus. It’s used mostly in continuous shooting mode for sports and action photography but can also be used for video.
Single shot AF mode
Here, the camera focuses once when you half-press the shutter release then holds that focus point until you press the button the rest of the way to take the picture. This is the usual mode for taking one photograph at a time (as opposed to continuous shooting).
Predictive autofocus
Here, the camera tracks subject in continuous autofocus mode and uses its movement within the frame and any changes in its distance from the camera to work where it’s going to be at the moment the shutter fires.
Phase detection autofocus
An autofocus system that checks the position of objects from two angles. If they don’t line up the object is out of focus – and the system can use the difference to work out how far to refocus the lens and in which direction. Phase detection AF sensors are used on DSLRs and now phase […]
Manual focus
Useful when you want to make the most of depth of field – with often means focusing between two objects rather than on one or the other. It’s also handy for ‘zone focusing’ in shoot-from-the-hip style street photography, where you want an instant shutter response.
Hybrid AF
Autofocus system that combines contrast autofocus and phase detection autofocus. It works using special phase-detection sensors built into the sensor. Contrast AF is typically slow but accurate, while phase detection AF is typically fast if potentially less accurate.
Focus points
Autofocus systems can focus at different points around the frame – the more advanced the autofocus system, the greater the number of AF points. You can either leave the camera to choose the autofocus point with ‘auto AF’ mode (or ‘auto area AF’) or select it yourself with single-point AF mode. Some cameras offer face-detection […]
Focus peaking
A special display mode designed to help with manual focusing when using an LCD display or electronic viewfinder. It exaggerates the edges of objects when they come into focus and can give a much more visible focus ‘snap’ than the regular display.
Focus mode
Camera autofocus systems work in one of three modes: single-shot autofocus (usually abbreviated to ‘S’), continuous autofocus (‘C’) and manual focus (‘M’). If you’re taking one photo at a time, use single-shot autofocus – the camera will focus once and then fire. If you’re using continuous shooting mode, use continuous autofocus – the camera will […]
Focus limiter
A switch found on some telephoto and macro lenses to restrict the autofocus to a specific range. This speeds up the autofocus for situations where you know you won’t need the lens’s full focus range.
Face detection
Some autofocus systems identify human faces within a scene and then adjust the focus and exposure for that face. It’s popular on compact cameras and is used on some DSLRs and mirrorless cameras too.
Electronic rangefinder
A feature which uses the camera’s autofocus mechanism to confirm focus even when you’re using manual focus mode. You turn the focus ring and the AF point lights up when the subject below it comes into focus. It can be useful when it’s hard to judge sharp focus by eye.
Contrast AF
A relatively simple autofocus system that measures the contrast around the edges of objects and then adjusts the focus to see if the contrast goes up or down. When the contrast is highest the subject is in focus. Contrast AF is accurate because it uses the image being captured by the sensor itself, but because […]
Continuous autofocus
In continuous AF (autofocus) mode, the camera continually refocuses all the time you have the shutter button half-pressed or fully-pressed. It’s used in continuous shooting mode to keep moving subjects in focus as you follow them with the camera. Continuous AF mode may include subject tracking or predictive autofocus capability.
Back button focus
Usually the camera will autofocus when you half press the shutter release button, but on more advanced cameras it’s possible to split off focus activation and assign it to a button on the back of the camera. Sports and action photographers generally find this a much more instinctive way to take pictures but it is […]