AH: The current AF system in EOS 1D Mark IV delivers excellent performance when photographing subjects like birds in flight against a varied background. In this case photographer often uses center point with a fixed number of expansion points, as opposed to color-tracking or automatic AF point/area selection given the erratic nature of the subject. What benefits does the new system bring in terms of speed and precision in this application?

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.

AH: We understand due to the large number of cross-type and double-precision cross-type sensors there was not enough room to fit the f/8 line sensor in the new AF sensor. However for wildlife applications the 2X Tele-extender in combination with f/4 super-telephoto lenses offers great flexibility. Is it possible for Canon to address this issue?

CW: This request has been conveyed for consideration.

AH: In practice the EOS 1D Mark IV AF system was superior to that of the EOS 7D in AI-servo with both f/4 and f/5.6 lenses despite having fewer cross-type sensors. How important are the cross-type sensors in AI-servo performance for a fast moving subject?

CW: Cross-type AF points increase the percentage of readable subject contrasts compared to single-axis sensors, but there are many other factors to consider when comparing overall AF system performance.

AH: Is it possible to toggle between the single/expansion/zone AF modes in 5D Mark III with the M-fn button in the same manner as the EOS 7D?

CW: Yes. On both cameras, you press the focusing point selection button first, then press the M.Fn button to change the AF point selection mode. Both cameras support Spot AF with all compatible lenses, Single Point AF, Selected point plus 4 adjacent points, Zone AF, and Automatic Focusing Point Selection using all AF points. However, because it has 61 AF points instead of 19, the EOS 5D Mark III also supports “Selected point plus 8 adjacent points” in addition to “Selected point plus 4 adjacent points.”

EOS 5D Mark III Auto Focus sensor

AH: We understand AF settings is vastly different between the EOS 5D Mark III/1DX and the previous EOS 1D Mark IV system. In addition to the presets tuned for a particular subject is it possible to adjust parameters such as AI-servo tracking sensitivity similar to the 1D MKIV?

CW: Yes.

AH: What is the combined shutter lag plus mirror blackout time in the EOS 5D Mark III?

CW: Shutter lag time is 59 milliseconds, the same as the EOS 7D, and considerably faster than the EOS 5D Mark II’s 73 milliseconds. Viewfinder blackout time is 112 milliseconds on the EOS 5D Mark III vs. 145 milliseconds on the EOS 5D Mark II.

AH: Given the increased burst speed why doesn’t the 5D Mark III support class 10 SD-UHS cards?

CW: The EOS 5D Mark III supports Class 10 SDXC and SDHC memory cards, but not the UHS standard.

AH: Increase of burst speed from 4fps to 6fps is significant and welcome, however, it still not adequate for some applications. Is Canon going to develop an 8fps or faster compact professional camera in near future or is that feature exclusive to the 1DX?

CW: no comment on Canon’s future plans or products.