Some cameras currently on the market are equipped with detachable lenses or sold without lenses, such as SLR or micro-SLR cameras. Such cameras can be equipped with different lenses according to different shooting demands and effects. But if the lens chosen has a different brand from the camera body or doesn't correspond to the specification of the camera body, the lens and the camera body are not matched. Typically photography professionals and enthusiasts may choose a professional Nikon (a brand name) SLR lens, but Nikon's SLR lens does not fit in all cameras, which has limited its application field. In such cases, a lens adapter can be adopted, one end of which is mounted with a lens and the other end of which is mounted on the camera body so that SLR lens can be installed in a greater variety of cameras through the lens adapter.
In most cases, a latch member is provided on the inside track of the manual aperture controlling ring in the lens adapter and plug and plugged with the lens aperture controlling rod, as the stroke of the lens aperture controlling rod on the lens is limited within an arc-shaped slot whose center is on the central axis of the lens and coincident with the central axis of the manual aperture controlling ring, the rotation angle of the manual aperture controlling ring is completely consistent with the moving angle of the lens aperture controlling rod. However, the moving angle of the lens aperture controlling rod is not linearly proportional to the opening-and-closing of the aperture blades (the change in size of the aperture), so the rotation angle of the manual aperture controlling ring is not linearly proportional to the change in size of the aperture. The aperture may change little when the rotation angle is large, or the aperture may change significantly when the rotation angle is small, which may lead to inconvenience for the user to control the change in size of the aperture through the manual aperture controlling ring.