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EOS 40D - AF sensor orientation

Doug Kerr

Doug Kerr

Well-known member
I think I saw someplace (!) that on the EOS 40D, certain of the cross-type AF sensors were oriented on a 45° basis.

Is this so, and if so, which ones?

This will probably be covered in the White Paper, when and if we get that for this machine.

Thanks.
 
Doug Kerr

Doug Kerr

Well-known member
EOS 40D - AF detector arrangement

The newly-released Canon EOS 40D White Paper (see link below) contains a nice description of the autofocus array of the camera. Here is my summary:

1. Each of the nine AF points is served by a cross-type detector (V/H orientation) supported at apertures of f/5.6 and larger.

2. In addition, the center point is served by a high-precision cross type detector ("diagonal" orientation) supported at apertures of f/2.8 and larger. The diagonal orientation is apparently intended to avoid conflict on the sensor chip between the elements of this detector and the elements of the other detector at the center point.

3. Regarding the cross-type detectors at the north, center, and south AF points, their horizontal-line-sensitive elements have two rows of sensels, staggered. This is intended to improve the performance of the system to gross misfocus. I suspect this means that it will be less likely that in the case of gross initial misfocus the system will have to hunt for a focus setting in which the degree of misfocus can be determined.

The paper comments that the AF calculation speed of the 40D is 1.3 times that of the 30D.

I have not yet found any assertions of AF "accuracy" for any of the detector types.

The White paper is available at:

http://www.the-digital-picture.com/White-Papers/Canon-EOS-40D-White-Paper.pdf

Thanks to Karl Günter Wünsch on dpr for the link.

Best regards,

Doug
 
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