The 19 cross-type AF points take advantage of the following technologies:
• With finer processing steps, the peripheral circuit could be made smaller and the
f/2.8 AF sensor area could be expanded
• The secondary image-forming lens (see diagram) is glass mold. By incorporating a
newly-developed aspherical surface on the lens, the focusing area of the f/2.8 light
flux could be expanded
As with the EOS-1D Mark II
N
, the center AF point is a cross-type sensor. It is vertical-line
sensitive with maximum apertures as small as f/4, and horizontal-line sensitive with
maximum apertures as small as f/8. If the maximum aperture of the attached lens or
lens/extender combination is f/4 or faster, high-precision,
cross-type focusing is possible. If the maximum aperture
of the attached lens or lens/extender combination is f/8
or faster, horizontal-line sensitive AF is possible.
Compared with the other 18 cross-type AF points, the
center AF point's focusing line width is larger while the
fill factor for each pixel is larger (f/2.8 field of view).
Also, the number of focusing lines increases along with
the brightness (f/5.6 field of view) to attain higher
pre-cision. Gross defocus is also detected. The camera
can also detect a grossly defocused subject 1.8 times
better than with the EOS-1D Mark II
N
.
V. INCOMPARABLE EOS AUTOFOCUS, NOW EVEN BETTER
17
Prime lens
Subject
Focusing plane
(Image plane)
Secondary image-forming lens
CMOS area sensor
: f/5.6 sensors
: f/2.8 sensors (Center AF point is f/4)
: Cross-type AF points
: Assist points
(Not user-selectable)
6.6
7.50
4.5
3.00
2.25
4.00
2.00
Sensor horizontal-line
sensitive at f/5.6
Sensor vertical-line
sensitive at f/2.8
Sensor vertical-line
sensitive at f/2.8
Sensor horizontal-line
sensitive at f/5.6
Previous 45-point sensor
EOS-1D Mark III
