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Chuck Westfall Interview
Canon’s Chuck Westfall interviewed with Arash Hazeghi about the 5D Mark III and what sets it apart from its predecessors. It’s an interesting read, and offers lots of insight into the improvements in sensor design as well as the all new autofocus system.
Mr Westfall breaks down the AF system
CW: The number and distribution of high-precision cross-type AF points has increased on the new 61-point AF system relative to the 45-point AF system used by the EOS-1D Mark IV. Moreover:
· The overall AF system speed of the EOS-1D X including lens drive is superior to that of the EOS-1D Mark IV on a lens for lens basis. The overall AF detection speed of the EOS 5D Mark III is superior to the AF detection speed of the EOS-1D Mark IV.
· The level of AF precision for 5 of the central area AF points on the 61-point sensor (i.e., the dual X-shaped cross-type points) is superior to the level of precision for any of the AF points on the 1D Mark IV.
· 21 cross-type AF points in the central area of the 61-point sensor are functional with maximum apertures as small as f/5.6; None (zero) of the cross-type points on the EOS-1D Mark IV are functional as cross-type sensors at maximum apertures smaller than f/4.
· The 61-point AF sensor has twice the low light sensitivity as the 1D Mark IV’s 45-point AF sensor (EV -2 vs. EV -1).
· The 61-point AF system supports AI Servo III, which is superior in subject tracking stability and consistency compared to AI Servo II found on the EOS-1D Mark IV.
· The 61-point AF system adds a greater degree of user control for subjects with various characteristics of acceleration and deceleration such as birds in flight.
· The 61-point AF system not only has 16 more AF points than any of the 45-point systems, it is also 20% wider in coverage (19mm vs. 15mm), making it easier for photographers to keep their subjects within the active AF area.