1D Mark II focusing vs 5D

[Mike_Kunitani]

I agree with EJP, the 5D AF system is both physically different, thus electrically different too. Look at page 6 of this document
http://www.photoworkshop.com/canon/EOS_Digital.pdf
One can see the 45 pt AF array is identical in both the 1DSmkII and 1DmkII and as a result the array fills up a larger proportion of the 1DmkII 1.3x crop frame. There are several other paragraphs about low light focus that may pertain to the hesitation in AF mentioned in this discussion (Pgs 9,10).

[AliceRhoden]

I keep hearing that the "AF array is identical" on the 1DSmkII and the 1DMkII. Why, then, does the 1DS MkII not exhibit the hesitation at the beginning of a focus cycle in low light as the 1D Mark II does?

In terms of low light focus acquisition, I have to rank the cameras this way

5D
20D
1DS
1DS Mark II

1D Mark II
D60

There's a gap between the 1DS Mark II and the 1D Mark II on purpose. The lag is noticable.

And no matter what the reason, I too find the lag unacceptable on a camera at this level and price point, especially one that is supposedly designed for fast action (poorly lit gymnasium, anyone?)

[E_J_Peiker]

[ QUOTE ]
I keep hearing that the "AF array is identical" on the 1DSmkII and the 1DMkII. Why, then, does the 1DS MkII not exhibit the hesitation at the beginning of a focus cycle in low light as the 1D Mark II does?

[/ QUOTE ]
As stated before, because the control logic is programmed differently.

[ QUOTE ]
... the 5D AF system is both physically different, thus electrically different too ..."

[/ QUOTE ]

From this quarter's issue of EOS Magazine:

"The EOS 5D has a new 9-point AF unit (similar to the 20D) with 6 supplemental AF points (all 6 clustered around the center AF-point), a new AF algorithm, and new AF circuitry.

This system improves subject detection and focusing precision at the center ... and significantly enhances subject tracking performance.

... the 6 supplemental AF points, which are grouped around the center (AF point), provide highly accurate focusing and do an especially good job of tracking a moving subject in the AI Servo AF mode.

(The) supplemental AF points are not visible in the finder and cannot be selected manually, but they can be seen in ZoomBrowser or ImageBrowser ... They are used during automatic AF point selection (AF calculation speed and accuracy are as good as, or better than, the 20D) and as AF area expansion points when the center AF point is selected (using) C.Fn 17-1. They do not function in One-Shot AF mode.

The center AF point has a special hybrid design. With f/2.8 or faster lenses, focusing is a 2-step process. First the f/5.6-sensitive cross-type sensor components are used to focus. When focus is almost achieved, a switch is made to the f/2.8-sensitive vertical line-sensitive sensors for high-precision focusing.

The center AF point's f/5.6 sensors each have 2 lines with individual pixels arranged in a zigzag pattern, making a total of 4 lines for horizontal line-sensitive focusing at the center.

... the center AF point can do a better job of detecting difficult-to-read, low-contrast subjects ...

All 6 supplemental AF points are at least f/5.6-sensitive. The 2 supplemental AF points directly above and below the center are also f/2.8-sensitive when a lens fo f/2.8 or brighter is used."


With all of the above noted, hopefully this may help to explain why some / many are noticing the improved focusing speed behavior of the 5D. It looks like the 5D's AF system is substantially different that either the 20D or the 1D/1Ds/1DM2/1DsM2 series.

Hope this helps.

Best regards,

Bill