Canon 40D - EOS 40D DSLR, Руководство по обслуживанию

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Technical Information
7
２）AF unit
To attain more stable AF performance than
before, the AF unit has more precise AF optics and
environment-resistant construction and materials.
(Fig. 012)
３）AF speed and focusing calculation
Compared to the EOS 30D, the focusing calculation speed is 1.3 times faster, and the AF
data-processing time is shorter. Despite the AF sensor's number of lines and the higher
number of pixels, AI SERVO AF at approx. 6.5 fps is attained.
４）AF modes
The AF modes are the same as the EOS 30D: One-Shot AF, AI Focus AF, and AI SERVO AF.
５）AI SERVO AF
Predictive AF can track a subject approaching at 50 kph up to about 8 m/26.2 ft away
with an EF300mm f/2.8L IS USM lens. Since 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.
６）Automatic AF point selection
The algorithm is the same as the EOS 30D's. However, with all AF points being cross-
type sensors, the subject detection is improved, making the AI SERVO AF subject-tracking
performance better. Also in the One-Shot AF mode, it increases the probability of capturing
the subject as intended.
７）AF-assist beam
The AF-assist beam is
a series of flashes. The
effective range is approx.
4 meters/13.1 feet at
the center AF point and
approx. 3.5 meters/11.5
feet at the eight off-
center AF points.
Secondary mirror
Main mirror
AF unit
Fig. 012 AF unit
Table 005 AF-assist beam with External Speedlites
Speedlite
Automatic
Selection
Manual Selection
Center
Top/
Bottom
Left/Right
Mid-left/
Mid-right
580EX II Yes Yes Yes Yes Yes
580EX Yes Yes Yes Yes Yes
550EX, ST-E2 Yes Yes N/A Yes Yes
430EX, 420EX Yes Yes Yes Yes Yes
380EX, 220EX Yes
＊
Yes N/A N/A N/A
* Focus can be achieved only with the center AF point.