soft focus lens and aperture disks
This is the homemade lens that I use most of the time.
Technically, it's 110 mm, four elements in three groups with a maximum aperture of about f/ 2. The elements are a -235 mm negative meniscus, a -167 mm negative meniscus, and a 2-element 75 mm achromat.
The aperture disks are used to control the amount of spherical aberration from the uncorrected lens. The lens and the top row of disks are loosely based on the Rodenstock Imagon.