Ten frames were shot on a tripod. For each frame, the 24/1.4G was defocused, then autofocus was allowed to complete. I always set my cameras to disallow shutter release unless the AF can lock on, so there is zero chance that the camera simply failed to focus.
The focus point was about 20 feet (6 meters) distant, a high-contrast sign with black lettering on white.
Unlike the exact-same scene with the Nikon D3s, the D3x had no trouble getting it right every time, which is even more puzzling given its failure to focus properly nearly every ad-hoc example.
Why should the D3s fail so miserably, and the D3x succeed, when both are seeing exactly the same thing under the same conditions? Perhaps there is something faulty about the lens. Or could the "Dynamic 51 point 3D Tracking" setting have something to do with it? I thought it might, but a follow-up test the next day to explore that idea produced no difference between the two settings.
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