Specifications Comparison of AF Sensors
40D
9 (All cross-type)
Cross-type sensor
cross-type sensor
high-precision f/2.8
compatibility
at center
Extreme-defocus
Yes
compatibility
EV range [EV]
14.4
Sensor pitch [µm]
The positioning of the AF points is almost the same as with the EOS 30D's AF sensor.
The center AF point has a cross-type AF sensor sensitive to vertical and horizontal lines
at f/2.8. This is a first in an EOS camera. Previously, the central sensor for f/2.8 or better
was only vertical-line sensitive. Because the f/2.8 sensor is a diagonal, cross-type sensor,
it does not obstruct the f/5.6 sensor positioned vertically at the center.
The upper center, center, and bottom 3 horizontal-line sensitive sensors are in a 2-line,
zigzag configuration. With this double focusing system, inconsistent focusing detection
is reduced. By using the 2-line focusing sensors described above, a subject in extreme
defocus can be detected and AF control is quick and easy.
To attain more stable AF performance than before, the
AF unit has more precise AF optics and environment-
resistant construction and materials.
The AF modes are the same as those of the EOS 30D:
One-Shot AF, AI Focus AF, and AI SERVO AF. Any of
these settings can be selected in Creative Zone shooting
modes. One-Shot AF is set automatically in the Portrait,
Landscape, Close-up, and Night Portrait modes. AI Focus AF (switches between One-Shot
AF and AI SERVO AF automatically) is set automatically in Full Auto and Flash Off modes.
Predictive AI Servo AF is set automatically in Sports mode. The EOS 40D can, of course,
also be focused manually in any shooting mode.
Compared to the EOS 30D, the EOS 40D's focusing calculation
speed is 1.3 times faster, and the AF data-processing time is
shorter. Predictive AF can track a subject approaching at 50
kph/31 mph up to about 26.2 ft./8m away with an EF
300mm f/2.8L IS USM lens.
Because subject detection has been improved with all
cross-type AF points, high-speed continuous shooting in
the AI SERVO AF mode is more stable than with the EOS 30D, and it is also done at a
faster framing rate (6.5 fps vs. 5.0 fps).
III. PERFORMANCE
Fig. 42 AF point position and spacing
AF Point Position and Spacing
30D
1 (Center)
Vertical-line
sensitive at center
–
-0.5 - 18
16
3.7
5.9
AF Unit
Fig. 44 AF unit
Main mirror
Secondary mirror
AF unit
Predictive AF Performance
Fig. 45 Predictive AF performance
100
[m]
20
10
8
1
5
10
50
100
Subject's speed
500
[Km/h]
11
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