The Voigtlander 75mm f1.8 Portrait Heliar is Voigtlander's first full-frame interchangeable lens with spherical aberration control, a large-aperture manual focus medium telephoto lens exclusively for mirrorless cameras. The lens focuses on the relationship between spherical aberration and bokeh and allows arbitrary control of under- and over- correction of spherical aberration to produce a wide variety of bokeh expressions.
The lens construction is of the HELIAR type with six elements in three groups and large aperture of F1.8 is achieved. Spherical aberration is controlled both by the spherical aberration control ring and by the aperture. In images under-corrected, the center of focus is soft-focus and flares in highlights. The rear bokeh is gently rendered. In over-corrected images, on the other hand, the centre of focus remains and the after-blur is bubbly. These tendencies have been regarded as defects that should be corrected from the point of view of ideal optical design, but this lens was planned and designed with the aim of making the characteristics of spherical aberration lead to unique photographic expression.
Fluctuating spherical aberration will, in optical principle, also shift the focus position, but this issue has been addressed by incorporating a mechanism that cancels out the misalignment by changing the distance between the lens groups in conjunction with the control ring. When operating the control ring, a small finger point is provided at the position where the left thumb touches it, allowing the approximate state of correction to be known tactilely.
This lens is equipped with electronic contacts and the lens usage status is reflected in the Exif information of the shooting data. It does not rely on the electronic lens optical compensation function in the camera, and the performance of the lens itself is captured in the image. The camera also has a built-in distance encoder. The built-in distance encoder is also compatible with models with 5-axis in-body image stabilization, which uses distance information to the subject for shift stabilization.
The viewfinder can also be enlarged by operating the focus ring. The minimum object distance is 0.7 m. Focusing is manual focus. The metal focus ring has a diamond pattern for excellent grip. The high-precision metal helicoid provides a silky, greased operating feel even when the focusing. The aperture is controlled by the lens, not by a command dial on the camera. The lens has a nine-element aperture, which allows the out-of-focus parts of point light sources to be rendered in a well-defined shape.
