An illustrated chronological story about how Canon autofocus systems and viewfinders went from a single AF point (1987) to 191 AF points (2020).
The AF points are arranged on multiple levels, expanding towards left and right as well as upper and lower regions of the viewfinder. As it is used on APS-C cameras, viewfinder coverage is fairly large.
Each AF sensor is indicated with a small frame. The center is shaped as a uniform square whereas the remaining eight AF sensors are rectangles, oriented depending on their sensitivity.
The sensor chip package has a similar structure to the package of the 7-point chip. A rectangular substrate with the active area is covered in transparent optical polymer. This particular AF sensor has introduced two innovative features that affect the central focus point: Horizontally, the center AF point uses four detectors, one pair at a standard distance from each other and one pair further apart. Vertically, the center AF point uses two parallel pairs of detectors that are installed in a dual-line zig zag arrangement. The purpose of this configuration is that the photoreceptor cells of the two lines are offset by half a cell pitch, effectively doubling the detector resolution. This not only increases the accuracy at which the phase alignment can be detected by the AF system but also allows better defocus detection. All the other AF points use linear sensors.
The center AF point is an f/5.6 standard-precision cross-type sensor (sensitive to both vertical and horizontal contrast lines) and f/2.8 high-precision horizontal sensor (sensitive to vertical contrast lines). Six AF points are vertical sensors (sensitive to horizontal contrast lines) and two AF points are horizontal sensors (sensitive to vertical contrast lines) as shown in the illustration. Autofocus is not possible during viewfinder shooting with lenses having maximum apertures slower than f/5.6.
The system has an AF working range of EV -0.5 - 18 at ISO 100.
This was the first AF system that had invisible and non-selectable assist AF points integrated. These are active only during AI Servo mode and they allow the camera to predict the focus condition for moving subjects. As this 9-point AF system is used on full frame cameras, viewfinder coverage is not as large as seen on the other 9-point systems.
Each AF sensor is indicated with a small frame. The center is shaped as a uniform square whereas the remaining eight AF sensors are rectangles, oriented depending on their sensitivity. In addition, there is a small spot metering circle around the center AF point.
The sensor chip package has a similar structure to the package of the first 9-point chip. The AF sensor features additional sets of detectors that do not correspond to visible AF points but to invisible Assist AF points. Dual-line zig zag arrangements were used for both vertical and horizontal components of the center AF point. Additional sets of f/2.8 high precision detectors have been used for the horizontal part of the center AF point and for two Assist AF points.
The center AF point is an f/5.6 standard-precision cross-type sensor (sensitive to both vertical and horizontal contrast lines) and f/2.8 high-precision horizontal sensor (sensitive to vertical contrast lines). Six AF points are vertical sensors (sensitive to horizontal contrast lines) and two AF points are horizontal sensors (sensitive to vertical contrast lines) as shown in the illustration. The two horizontal Assist AF points (sensitive to vertical contrast lines) are f/5.6 standard-precision sensors but turn into f/2.8 high-precision sensors when an f/2.8 or faster lens is attached to the camera. The four vertical Assist AF points (sensitive to horizontal contrast lines) are f/5.6 standard-precision sensors. Autofocus is not possible during viewfinder shooting with lenses having maximum apertures slower than f/5.6.
The system has an AF working range of EV -0.5 - 18 at ISO 100.
This was the first of Canon's autofocus systems that had a dual cross-type autofocus detector installed. This dual cross-type sensor allows the camera to use high-precision focusing when an f/2.8 or faster lens is used. It was also the first AF system with multiple AF points all being cross-type sensors.
Each AF sensor is indicated with a small frame. In addition, there is a small spot metering circle around the center AF point.
The sensor chip package has a similar structure to the package of the previous 9-point chips. In order to enable cross-type capabilities to all AF points, this AF system uses an increased number of detector lines, particularly in the left and right zones. At the center, two pairs of dual-line zig zag detectors are placed vertically on the active area. These are jointly used by three AF points (the one on the top, at the center, and at the bottom). One new feature stands out: This sensor for the first time has a complete cross of high-precision detectors (✕-shape) that is arranged vertically around the center area of the active area.
All AF points function as standard-precision cross-type sensors (sensitive to both vertical and horizontal contrast lines) that are designed for use with lenses having a maximum aperture of f/5.6 or faster. The center point turns into a high-precision dual cross-type (sensitive to four contrast line orientations) with f/2.8 or faster lenses. Note that certain lenses may reduce some cross-type AF points to vertical-line or horizontal-line sensitive only (see the camera's instruction manual for details). Autofocus is not possible during viewfinder shooting with lenses having maximum apertures slower than f/5.6.
The system has an AF working range of EV -0.5 - 18 at ISO 100.