Like many mirrorless cameras, the Leica X Vario has a fundamental algorithmic flaw in its autofocus: it focuses with the lens stopped down to the shooting aperture. Compare that idea with opening the lens diaphragm to focus precisely, then shooting at the stopped-down aperture (as with all DSLR cameras).
This stopped-down autofocus algorithm not only affects focus accuracy, it actively degrades autofocus performance as the lighting dims, a problem I encountered repeatedly in the field. At times, the focus was unable to lock on at all unless I opened the aperture fully.
With the lens stopped down, a deeper zone of sharp focus is obtained (depth of field), and the camera cannot then distinguish the optimal focus, with the result that the near-far positioning of the zone of focus can be skewed in undesirable ways: a blurry foreground and too-sharp background or vice versa—all while the chosen point of focus is just as sharp either way (or maybe not, as we shall see).
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