The parameter 
is used to test the hypothesis that a certain number
of spots belong to one conic. If 
is low, e.g. 
a lot of
planes will be accepted, among which incorrect ones. If 
is high,
e.g. 
, only a few planes will be formed, but most of them will be
correct.
format qmin
default qmin 0.10 example qmin 0.25