Kase Optics, a Chinese company primarily known for its filter systems, has expanded its lens lineup with the 150mm f/5.6 AF, a reflex lens — also referred to as a mirror or catadioptric lens — designed for mirrorless camera systems.

The lens, first shown publicly at the CP+ Camera and Photo Imaging Show in Yokohama, Japan, is offered in Nikon Z, Sony E, and Canon EF mounts. A manual-focus-only version is planned for Canon RF mount, as Canon’s licensing restrictions prevent third-party autofocus lenses on that system. The Canon EF mount version, while technically compatible with Canon’s older DSLR system, is not supported on RF-mount bodies. Finally, a GFX mount version for Fujifilm medium-format cameras is also in the lineup.

This is Kase’s second reflex lens, following the 200mm f/5.6 MF released in 2024. The 150mm model represents a notable departure from that predecessor in one key respect: it incorporates autofocus. In fact, autofocus implementation in reflex lenses is exceptionally rare due to the complexity of the mirror-based optical system: the only broadly comparable precedent is the Minolta — later Sony — 500mm f/8 AF reflex lens produced for A-mount SLR cameras. The Kase 150mm f/5.6 AF uses an internal motor to drive its autofocus mechanism and also supports in-body image stabilization on compatible camera bodies. The minimum focusing distance is 1.5 meters, and an AF/MF switch on the barrel allows manual override.

The optical construction consists of five elements arranged in four groups. Like all reflex lenses, it has no adjustable aperture diaphragm, making f/5.6 the sole available aperture across all shooting conditions. The front filter thread measures 67mm and is compatible with Kase’s magnetic filter system, and a USB-C port is included for firmware updates. The body is constructed from aluminum alloy and features a grooved focus ring.

Kase also claims that at 150mm, this is the shortest focal length at which a reflex lens has been produced, a segment of the market where most manufacturers historically targeted much longer focal lengths to maximize the size and weight advantages of the mirror-based design while keeping costs low. At 150mm, the lens sits within portrait telephoto territory, a context where the fixed aperture and unconventional bokeh shape may be more or less appropriate depending on the photographer’s aesthetic preferences. Kase appears to be positioning the donut bokeh produced by the lens as a deliberate stylistic characteristic of its reflex lens range, following a similar approach from brands like TTArtisan, which have also explored this niche in the mirrorless era.

Here are some sample pictures, courtesy of Kase, shot with the company’s 200mm f/5.6 Reflex lens (not the 150 f/5.6 AF), with the donut bokeh well visible: