[metapost] How to use a thinner pen?

[Taco Hoekwater]

Rodolfo Medina wrote:
> It seems that I don't manage to use a pen thinner than the default 0.5bp.
> When I give the command: `pickup pencircle scaled 0.1bp', or even `pickup
> pencircle scaled 0.0000001bp', my eye can't notice any difference with the
> default thickness.  Instead, a bigger thickness works fine.  What am I
> missing?
> 
> Thanks for any help.

You should be able to pick up a smaller pen.  Please post an example
input file, so we can have a look. Also, how exactly do you view the
output?

Best wishes,
Taco