This 60 mm f/1.8 lens is designed for creating a portrait image with a background of "swirling" bokeh and vignetting.
The bokeh rotates around the center of the frame and draws attention to this part, as if the middle is surrounded by concentric circles. This effect becomes even more obvious and interesting when shooting at points of variable illumination and contrast, for example, in street portraits in low light, against the background of forests and industrial buildings.
Vignetting has the same effect of drawing the eye to the center. The level of bokeh and vignetting is controlled using the slider on the lens frame.
The aperture range from f/1.8 to f/2.8 provides a so-called soft effect, then from f/2.8 there is an increase in sharpness.
Maximum sharpness is achieved on Canon SLR cameras.