The Duclos PL macro tube set decrease the M.O.D. (Minimum Optical Distance) of a PL-Mount lens to obtain similar images to macro lenses without sacrificing image quality with a low brightness loss.
These tubes can be used with Super 35mm or Full Frame lenses and cameras, nor with anamorphic lenses.
Estimate magnification rates:
Tube (mm) / Lens focal length (mm) = Magnification factor
Indicative brightness loss:
0.1- 0.2x = 1/2 stop
0.25-0.33x = 1 stop
0.5x = 1.5 stops
1x = 2 stops
A 85mm lens with a 35mm Duclos PL macro tube:
35/85 = 0.41x magnification and 1.5 stops brightness loss