An illustrated chronological story about how Canon autofocus systems and viewfinders went from a single AF point (1987) to 191 AF points (2020).
The number of AF points was increased, resulting in a 45-point AF system. Seven of these are high-precision cross-type AF points. Having this quantity of focusing points not only increases the flexibility in placing the focus within the image but it also improves the reliability of AI Servo focus tracking as the subject is more likely to be picked up by adjacent AF points.
Each AF sensor is indicated with a rectangular frame. AF points are arranged in a large oval pattern as shown in the illustration. The viewfinder coverage depends on the camera model. The illustration shows the viewfinder coverage of an APS-H camera where the AF points cover a fairly large portion of the image. On full frame cameras, a smaller portion of the viewfinder is covered.
This chip uses a ceramic package measuring 21.2 mm × 13.6 mm. The top is covered by clear glass. In contrast to previous sensor layouts, this chip does not feature distinct pairs of detector lines but rather rectangular arrays with countless tiny parallel detector lines embedded. The two larger dark rectangles are the vertical sensor arrays and the smaller dark rectangles are the horizontal detector arrays. This AF system requires comparatively large separator lenses. The two vertically aligned lenses cover all of the large detector arrays and the two horizontally aligned lenses cover the small detector arrays.
All 45 AF points are standard-precision vertical detectors (sensitive to horizontal contrast lines) designed for lenses having a maximum aperture of f/5.6 or faster. A row of seven AF points turns into high-precision cross-type detectors (sensitive to both vertical and horizontal contrast lines) if a lens with maximum aperture of f/2.8 or faster is attached to the camera. With cross-type autofocus enabled, vertical-line detection is about three times as sensitive as horizontal-line detection. For the center AF point, high-precision vertical-sensitive AF detection is even possible with lenses having a maximum aperture of f/4, and standard-precision horizontal-sensitive AF detection is even possible with lenses having a maximum aperture as small as f/8. With lenses having maximum apertures slower than f/8, autofocus is not possible during viewfinder shooting.
The system has an AF working range of EV 0 - 18 at ISO 100.
Compared to the previous 45-point AF system, the number of high-precision cross-type points was increased to 19.
Each AF sensor is indicated with a rectangular frame. AF points are arranged in a large oval pattern as shown in the illustration. There are 19 user-selectable AF points that are displayed with full opacity. The 26 Assist AF points are not selectable by the user and are displayed with reduced opacity.
This chip uses a ceramic package measuring 21.2 mm × 13.6 mm. The top is covered by clear glass. The actual detector lines are arranged in four rectangular dark zones as shown in the illustration. The separator lenses are comparatively large (same as previous type).
This AF system has 26 vertical Assist AF points and 19 high-precision cross-type points. The Assist AF points are standard-precision horizontal-sensitive only and are designed for lenses having a maximum aperture of f/5.6 or larger. The cross-type points are horizontal-sensitive to f/5.6 or faster and vertical-sensitive to f/2.8 or faster. With high-precision cross-type autofocus enabled, vertical-line detection is about two times as sensitive as horizontal-line detection. For the center AF point, high-precision vertical-sensitive AF detection is even possible with lenses having a maximum aperture of f/4, and standard-precision horizontal-sensitive AF detection is even possible with lenses having a maximum aperture as small as f/8. With lenses having maximum apertures slower than f/8, autofocus is not possible during viewfinder shooting.
The system has an AF working range of EV -1 - 18 at ISO 100.
Compared to the previous 45-point AF system, the number of high-precision cross-type points was increased to 39.
Each AF sensor is indicated with a rectangular frame. AF points are arranged in a large oval pattern as shown in the illustration. There are 6 vertical-only AF points that are displayed with reduced opacity. During manual point selection, all AF points are user-selectable and 39 cross-type points are available. However, these are reduced to 19 cross-type points during automatic point selection (with the remaining 26 AF points turning into vertical sensors).
This chip uses a ceramic package measuring 21.2 mm × 13.6 mm. The top is covered by clear glass. The actual detector lines are arranged in four rectangular dark zones as shown in the illustration. The separator lenses are comparatively large (same as previous type).
All 45 AF points are standard-precision vertical detectors (sensitive to horizontal contrast lines) designed for lenses having a maximum aperture of f/5.6 or faster. A total of 39 AF points turn into high-precision cross-type detectors (sensitive to both vertical and horizontal contrast lines) if a lens with maximum aperture of f/2.8 or faster is attached to the camera and manual point selection is used. With high-precision cross-type autofocus enabled, vertical-line detection is about two times as sensitive as horizontal-line detection. For the center AF point, high-precision vertical-sensitive AF detection is even possible with lenses having a maximum aperture of f/4, and standard-precision horizontal-sensitive AF detection is even possible with lenses having a maximum aperture as small as f/8. With lenses having maximum apertures slower than f/8, autofocus is not possible during viewfinder shooting.
The system has an AF working range of EV -1 - 18 at ISO 100.
Compared to earlier generations of AF systems, both the viewfinder coverage and AF point density have increased. All of the 45 AF points offer standard-precision cross-type autofocus capabilities.
Each AF sensor is indicated with small rectangular frames. AF points are arranged in three large rectangular zones. The illustration shows the viewfinder coverage offered by an APS-C camera. The coverage is smaller on a full frame camera.
The sensor uses the rectangular design that is covered in transparent optical polymer. The three zones of detector lines are clearly visible. The center area uses vertical lines with the zig zag arrangement to increase the autofocus accuracy. In general, the image shifts in phase detection systems are extremely small, even on the f/2.8 detectors. For this reason, dual-line zig zag detectors have also been used for the diagonal high-precision cross-type detector, increasing the resolution and therefore detection accuracy of the f/2.8 diagonal cross.
All AF points are standard-precision cross-type sensors designed for lenses having a maximum aperture of f/5.6 or faster. The center AF point turns into a high-precision dual cross-type sensor when an f/2.8 or faster lens is attached to the camera. For the center AF point, standard-precision cross-type AF detection is even possible with lenses having a maximum aperture as small as f/8. Depending on the lens attached to the camera, the number of usable AF points, AF point patterns or the types of AF sensors may vary. With lenses having maximum apertures slower than f/8, autofocus is not possible during viewfinder shooting.
The system has an AF working range of EV -3 - 18 (with the center AF point supporting f/2.8) at ISO 100.