MORE TESTS ...
When the 85mm PC is fully tilted
its advantage is notable due to the change of the focus plane,
specially at medium apertures. Evaluation of test results
is more complex since diffraction plays an important role
in both lenses, reducing perceptible differences.
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Comparative
DOF around the minimum working distance for the 105mm
f/2.8D AF and the 85mm f/2.8D PC Micro Nikkor unshifted
and untilted.
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The graph above shows the theoretical
DOF data, as supplied by Nikon when both lenses are focused
at a working distance of 40 cm or 15.7 inches, at the range
of nominal apertures. The depth of field of the 105mm Micro
Nikkor is bigger than that of the 85mm; however, one should
not forget we are looking at fractions of decimals in centimeters,
i.e. millimeters. This differences grow bigger at close-down
apertures: at f/32 the DOF of the 105mm is 1.3cm vs 0.9cm
on the 85 PC.
Now, when DOF is compared for longer
distances, it becomes evident the small advantage of the 105mm
only exists at short working distances.
In the graph below, each pair of
lines of the same color compares DOF for both lenses at the
same working distance, at different apertures (in the X axis),
expressed in centimeters at the Y axis. The longer line of
each pair belongs to the 85 PC since it reaches f/45.
Interesting to notice is how at
f/32 and 100cm (one meter) from the subject, the 85 PC surpasses
the 105 lens by almost 5cm (2"): with a DOF of 19.5cm
against just 15.4cm.
The shift and tilt lens can reach
even further at f/45; DOF is then 28cm / 11 inches. This aperture
is nevertheless not advisable due to the diffraction at such
close down aperture.
Of course all of the above corresponds
to the 85mm without shift or tilt.
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