This page establishes a baseline for understanding just how important focus accuracy is to exploiting the 24+ megapixels of the Nikon D3x. The goal is not any absolute metric, but rather simply to show that small focus differences (eg 1% of the subject distance) can produce subjectively quite different results, with high or lower contrast and more or less color fringing.
A resolution target was photographed at a distance of approximately 9 feet (2.7 meters) at a reproduction ratio of approximately 1:24. A tripod, mirror lockup and remote release were used on the D3x. Live View was used to focus wide open at f/2 on the Zeiss ZF 100mm f/2 Makro-Planar, zoomed in maximally for the best possible accuracy.
As seen below, the target shows some vignetting at f/2, and some uneven illumination (numerous Solux bulbs for near-daylight). We are concerned only with the center portion.
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The well-used target. The strip of center patches is stacked, for “depth”.