Schneider Optics PC-SUPER-ANGULON 28 mm f/2.8 - Manual (Page 8)

8 Large Image Circle for Lens Shifts up to 1¡ mm
The PC-SUPER-ANGULON 28 mm f/2 .8 already produces an exceptionally
flattened image at full aperture within the 62 mm image circle which is thus
twice as large in area relative to the image circles of other 35 mm lenses .
Sharpness and contrast are increased further in the central area used with-
out shift by stepping down slightly to f/4 to f/5 .6 . Sharpness, contrast and
brightness naturally drop outside this area due to the huge image angle
with an open aperture . The full aperture with a decentered lens is there-
fore only intended for the image composition and the focusing . A good im-
aging performance is obtained at the edge when stepping down further in
dependence on the adjustment path; an aperture of ¡1 is recommended at
maximum shift . Distortion and vignetting are exceptionally low .
While the image quality falls considerably in the close range with many
wide-angle lenses, the good imaging properties of this lens are maintained
thanks to “floating elements” (a distance-coupled axial shift of a lens ele-
ment group relative to the remaining system) . This makes this lens very in-
teresting e . g . for model shots .
The adjustment takes place at a shifting knob on a flexible shaft which is
easy to grip and sensitive in operation . Millimeter scales on mutually oppo-
site sides allow comfortable reading in any shifting knob position . Since the
shift is possible at both sides of the zero position, the most favorable ori-