The Uno barrel lens is glued into a short M42 macro extension tube.
Aldis Uno Anastigmat Series III f/7.7 5 inch
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A Soft Focus and Bokeh Experiment
Having read about the Taylor, Taylor & Hobson Portrellic lens with
variable softness obtained by adjusting the distance between the lens groups,
I decided to test this idea with the Uno. The threading of the lenses doesn't
allow very much movement, but unscrewing both the front group and the back
element increased the distance by about 3-4mm. There was only a very
slight softening at focus, but the bokeh softened somewhat, approaching ideal.
The result is very pleasant and balanced in a hard to define way.