No I’m not talking about the backfocus problem seen with autofocus lenses. I’m talking about consistent backfocus using manual (eye) focus with any lens I try. My left eye agrees with the focus confirmation indicator inside the Nikon D3 viewfinder (at least when the focused area is unambiguous). The error is such that it results in throw-away results, very frustrating because I often shoot wide open, especially with Zeiss ZF Lenses, which offer outstanding performance there.
The Nikon D3 thinks the image at top is in focus, according to the focus confirmation indicator inside the viewfinder. And so does my left eye. The image at bottom was focused with Live View.
Nikon D3—eye focus (top), Live View (bottom), 100mm @ f/2, 1/4000 sec
I’m beginning to wonder if there can be some internal oddity, say a loose part that moves a few microns when the camera is tilted up or down, because in the field I can reproduce the problem at will with a wide variety of subjects (dozens) with different lenses of different focal lengths. This is no focus shift (spherical aberration) issue; the lenses are focused and shot wide open. Under controlled conditions with a high contrast target (limited testing) focus is accurate sometimes, but when an error occurs (frequently), it’s always backfocus.
I shot the same lenses on the Canon EOS 1Ds Mark III (using an adapter) and could not produce the problem—not once, establishing that the problem lies with the camera body, not my eyes. I’m left to conclude that my Nikon D3 is defective somehow (eg out of alignment). If the optical path from the lens to the sensor were not identical as the one from the lens to the viewfinder, that would explain things. The D3 might have to go into Nikon for a checkup.
Zeiss ZF 100/2 Makro-Planar @ f/2